Auditory processing: how the brain hears

Perception and sound character

Answers on this topic

• Which kinds of error does Rob consider audible, and which does he consider benign?
• Why does Rob distinguish perception from hearing, and why does he distrust psychoacoustic thresholds?

Everything he said on this topic (218)

One-line summaries in our words, oldest first. Each link opens the original.

• 2014-04-17Watts says content above 22.05 kHz is inaudible (he hears to 16 kHz) but 4uS transient timing matters, and describes a planned pulse array ADC with multiple sample-rate outputs. Head-Fi, Apr 2014
• 2014-06-03Watts says blanket claims like "native DSD is best" are usually wrong, that audio is too complex to judge without careful AB listening tests, and that such tests overturned his own assumptions. Audiophile Style, Jun 2014
• 2014-06-21Watts distinguishes pitch resolution from the 4uS inter-aural delay, and argues sample rates matter for transient timing, so a good interpolation filter makes CD sufficient. Head-Fi, Jun 2014
• 2014-08-24Watts says some audible distortions are unmeasurable yet measurements matter, extra amps degrade transparency, and transparency aids musicality through variation and reduced brain strain. Head-Fi, Aug 2014
• 2014-10-20On Hugo's first anniversary, Watts recalls its first listening test, credits a six-year Verilog rewrite and the Spartan-6 FPGA, and says pursuing transparency paid off in musicality. Head-Fi, Oct 2014
• 2015-02-02Watts says the fun of his job is finding improvements, and he is amazed how small errors must be before they become inaudible to the brain. Head-Fi, Feb 2015
• 2015-05-20Watts says he finds it very bizarre and cannot accept that the brain requires a 350 dB performance level. HIFICLUBE.NET JVH 8:35
• 2015-05-20Watts says the depth is accurate, not added reverb: dry recordings stay at the speakers. He is unsure whether 350 dB is truly needed or an analog mechanism explains it. HIFICLUBE.NET JVH 9:00
• 2015-12-11Watts defines musicality as emotional involvement, achieved by reducing errors the brain cannot decode: timing (long taps), small-signal accuracy for depth (2048FS noise shapers), and noise floor modulation. Head-Fi, Dec 2015
• 2016-03-28Watts's first blog post sets out his listening-test method and nine attributes to judge, argues the brain resolves errors below hearing thresholds, and defines musicality as emotional engagement. Head-Fi, Mar 2016
• 2016-04-28Watts speculates that hunters evolved precise auditory depth placement, to about a foot, because locating prey by sound mattered for survival. Head-Fi, Apr 2016
• 2016-07-09Watts describes brain break-in as gradually improving perceived depth and note starts and stops, citing depth returning a month after adding a bookshelf, while smoothness changes are hardware. Head-Fi, Jul 2016
• 2016-07-24Watts says timing accuracy is important for timbre, and the ear judges bass pitch from the starting transient, citing experiments where removing it made a bass guitar's pitch unidentifiable. Hifistatement 2:12
• 2016-07-24Watts says studying sampling theory in the early 1980s showed him long tap lengths were needed to recover timing, which he knew mattered for perception, though he then hated digital. Hifistatement 0
• 2016-07-24Watts says for DAVE he raised noise shaper performance from Hugo's 200 dB through 220, 240 and 260 dB, depth improving each time, reaching -350 dB over 90 days. Hifistatement 3:05
• 2016-07-24Watts says the brain detects tiny errors as poorer instrument placement, depth needs perfect accuracy, and he ended with a new 17th-order noise shaper with 46 integrators. Hifistatement 3:54
• 2016-07-24Watts says redesigning DAVE's all-digital noise shapers to 350 dB gave the same results, so the digital path truly needs 350 dB (48-bit) accuracy; it is not a proxy. Hifistatement 5:24
• 2016-08-19Watts hypothesizes that brain break-in, first noticed with Hugo, is the brain unlearning coping strategies for sampled-data timing errors, which DAVE showed must be accurate to nanoseconds. Head-Fi, Aug 2016
• 2016-10-18Watts says DAC differences are night and day to him, describes a well-regarded DAC sounding awful, and wonders whether others' systems, his own bias or differing sensitivities explain disagreement. Head-Fi, Oct 2016
• 2016-12-11Watts says a 33-ohm load barely changes DAVE's THD+N (-127 to -124 dB), and argues a wider soundstage usually signals lost depth and transparency, except where recordings encode out-of-the-box cues. Head-Fi, Dec 2016
• 2017-09-19Watts explains headphone depth perception, why Hugo 2 crossfeed gives out-of-head sound, and why small-signal accuracy to -301 dB lets the brain use depth cues. Head-Fi, Sep 2017
• 2017-10-13Watts says the talk covers how a DAC's interpolation filter reconstructs timing, starting with perception: only 10 percent of vision comes from the eyes, 90 percent from the brain. miceblue425 43
• 2017-10-13Watts says what we hear is the brain's processing rather than the ears' output: the brain separates sounds and tags each with a location in space. miceblue425 1:28
• 2017-10-13Watts says the perceived audio scene is created entirely in the brain by processing nobody understands, citing a person's ability to separate several talkers at a party. miceblue425 2:15
• 2017-10-13Watts describes hearing performers three feet apart in depth at a concert with eyes shut, calls the brain's depth placement extraordinary, and says high-end audio does not understand this processing. miceblue425 3:00
• 2017-10-13Watts says design normally ignores errors below psychoacoustic thresholds, but he has heard errors at -140 to -150 dB, well below the threshold of audibility. miceblue425 3:50
• 2017-10-13Watts says tiny errors interfere with the brain's processing, so whenever he detects, measures or simulates an error he listens and reduces it until he hears no difference. miceblue425 4:35
• 2017-10-13Watts says the chip engineers he worked with never discussed sound quality, only measurements, then introduces the interaural delay neurons linking the left and right ears. miceblue425 5:42
• 2017-10-13Watts says the interaural neuron delay is about 4 microseconds, known from 1950s cat experiments and human phase-shift tests, and lets the brain place sounds within two degrees. miceblue425 6:25
• 2017-10-13Watts says depth cues include the natural attenuation of sound by air and reverberant detail, and that the 4 microsecond threshold implies the brain processes at a 250 kHz sampling rate. miceblue425 7:18
• 2017-10-13Watts says the ear is poor at bass, so a bass guitar's pitch is followed from its initial transient; with the transient removed it becomes a low-frequency lump of noise. miceblue425 8:04
• 2017-10-13Watts concludes that transients are very important for perceiving the pitch of bass. miceblue425 8:45
• 2017-10-13Watts says timbre depends on transients, and that pitch, soundstage, timbre and the starting and stopping of notes all come from transients, which digital audio's frequency-response focus neglects. miceblue425 8:53
• 2017-10-16Watts posts his second seminar on DACs: noise shaper listening tests showing sub-threshold errors affect depth, a 350 dB accuracy need, chip DAC limits, DSD and pulse array analog benefits. Head-Fi, Oct 2017
• 2017-10-20Watts says a DAC's purpose is to reproduce the analog signal inside the ADC, that conventional DACs reproduce transient timing poorly, and that the brain constructs what we hear. Hifistatement 0
• 2017-10-20Watts says the brain separates sounds, places them in space and judges their timbre in ways science cannot explain, using timing cues such as the interaural delay. Hifistatement 43
• 2017-10-20Watts says interaural neurons have about 4 microseconds accuracy, far finer than CD, and that transient timing governs perceived starting and stopping of notes, timbre and bass pitch. Hifistatement 1:30
• 2017-10-20Watts says the brain gets bass pitch from the starting transient, so losing it on a bass guitar makes the tune impossible to follow, and timing is crucial. Hifistatement 2:13
• 2017-12-05Watts says there is no understanding of how the brain processes audio or separates sounds, and that psychoacoustic thresholds have no bearing on that brain processing. RMAF 54
• 2017-12-05Watts says audibility cannot be assumed and needs careful structured listening tests, and that chip designers work to a marketing specification without listening, calling audiophiles 'audio fools'. RMAF 1:41
• 2017-12-05Watts says higher-order harmonics and anharmonic distortion are very audible because the brain subtracts the ear's own harmonic distortion but cannot subtract anharmonics, which do not occur naturally. RMAF 12:07
• 2017-12-09Watts says what fascinates him is how minute distortions can be highly audible given the ear/brain's extreme sensitivity, requiring extreme lengths and long development to improve musicality. article, Dec 2017
• 2018-01-16Watts says the ear/brain keeps proving more sensitive than expected; the M scaler gives better than 16-bit accuracy at 16FS, and Davina will show whether that is enough. Head-Fi, Jan 2018
• 2018-01-30Watts lists ways amps add bass bloom (2nd harmonic, low damping, coupling-cap dielectric absorption), says Hugo 2 avoids all three, and advises EQ or better headphones instead. Head-Fi, Jan 2018
• 2018-02-23Watts says the brain uses transients for interaural delay, with neurons resolving about 4 microseconds, far finer than CD's 22 microseconds, to locate sounds left to right. MajorHiFi 4:56
• 2018-02-23Watts cites experiments where removing starting transients made trumpet and piano hard to tell apart, saying transients are key to timbre and pitch and the ear is poor at bass. MajorHiFi 5:43
• 2018-02-23Watts says the brain reconstructs limited ear information into perception, judges bass pitch from the starting transient, and that without it a bass guitar's rhythm cannot be followed. MajorHiFi 6:28
• 2018-02-23Watts says transients shape perceived imagery, timbre and pitch, that the interpolation filter recovers timing, and that theory allows perfect recovery of a bandlimited signal at any sample rate. MajorHiFi 7:07
• 2018-03-16Watts attributes reduced loudest-instrument dominance to no noise floor modulation and the WTA filter, says an M scaler enhances it, and calls dominance a major cause of fatigue. Head-Fi, Mar 2018
• 2018-04-04Watts says since Hugo bad recordings became enjoyable, concluding the brain copes with noise, harmonic distortion and frequency response but not digital's unnatural distortions. Head-Fi, Apr 2018
• 2018-07-21Watts opens his talk on why the M Scaler has a million taps, saying timing is an essential perceptual cue for the brain, with transients central to it. c w 4:25
• 2018-07-21Watts defines a transient and says interaural-delay neurons measure left-right timing differences to about 4 microseconds, letting the brain place images within a two-degree angle. c w 5:08
• 2018-07-21Watts says the 4 microsecond perception threshold is much finer than CD's 22 microseconds, and that removing a bass guitar's starting transient makes its pitch hard to hear. c w 5:51
• 2018-07-21Watts says the ear is a poor transducer for bass, so the brain calculates bass pitch, and without the transient the bass line cannot be followed. c w 6:33
• 2018-07-21Watts says transients are essential to timbre, citing experiments where removing transients made trumpets and pianos almost impossible to tell apart. c w 6:54
• 2018-07-21Watts says digital audio's principal problem is the timing of transients, from which we perceive pitch, left-right soundstage, timbre and the starting and stopping of notes. c w 7:49
• 2018-07-21Watts says CD samples are 22 microseconds apart, the brain is very sensitive to timing errors, and digital reconstructs transients slightly early or late depending on sampling and surrounding music. c w 8:27
• 2018-07-26Watts posts his CanJam presentation: transients cue placement, pitch and timbre; conventional filters mistime them; 1M WTA taps match sinc to 16.6 bits using 528 DSP cores. Head-Fi, Jul 2018
• 2018-08-06Watts says the brain uses transient information for location, timbre and pitch, and recounts a listener saying the M Scaler made the tempo sound slower, which he relates to flow. Pursuit Perfect System 2:47
• 2018-08-10Watts describes hearing a Florida thunderstorm, marveling at how precisely perception locates sounds, and says reproduced sound still falls short of live unamplified sound. Head-Fi, Aug 2018
• 2018-09-27Watts distinguishes perception from hearing, argues brain correlation exposes errors below noise, and recounts a single-blind -180 vs -200 dB noise shaper test an engineer heard easily. Head-Fi, Sep 2018
• 2018-12-13Watts describes the brain's interaural delay: a chain of neurons between the ears, each delaying about 4 to 6 microseconds, firing when left and right signals coincide. Pursuit Perfect System 39
• 2018-12-13Watts cites 1950s cat experiments and human phase-shift listening tests as evidence for the 4 microsecond interaural cue, which he says implies the brain works to about 250 kHz. Pursuit Perfect System 1:25
• 2018-12-13Watts contrasts CD's 22 microseconds with the brain's 4 microseconds, saying this explains why high definition and the WTA filter work, and says the brain infers bass from transients. Pursuit Perfect System 2:15
• 2018-12-13Watts says psychoacoustic tests show that removing transient information stops listeners following bass pitch or telling a trumpet from a piano, and that digital's problem is reconstructing transient timing. Pursuit Perfect System 3:04
• 2018-12-13Watts says modulated transient timing confuses the brain, degrading bass, timbre, pitch, separation, focus and spatial location, and blames limited processing before starting a tone-burst illustration. Pursuit Perfect System 4:38
• 2019-01-29Watts says finite filters trade oversampling rate against data, that 4 uS interaural resolution proved insufficient, and that high rates matter for transient timing accuracy, not hearing 768k. Head-Fi, Jan 2019
• 2019-03-01Watts suggests anechoic chambers feel disconcerting because the brain builds an acoustic footprint of its environment and gets a null result there. Head-Fi, Mar 2019
• 2019-06-14Watts says Davina hit hardware and decimation-filter problems, argues audible timing errors are non-linear ones, and cites WTA 2 tests as evidence of sensitivity below the 7-4 uS interaural limit. Head-Fi, Jun 2019
• 2019-12-16Watts says 200 to 350 dB differences are so tiny he risks being called a lunatic for calling them audible, and does not understand why the brain is so sensitive. Passion for Sound 14:20
• 2019-12-16Watts says we know the brain's depth cues but not how it locates instruments in space, so audibility cannot be asserted either way. Passion for Sound 15:05
• 2019-12-19Watts says a sinc function needs infinite processing, and that transients matter because the brain uses them, e.g. interaural delay sensed by a chain of neurons to locate instruments. Passion for Sound 1:50
• 2019-12-19Watts says left-right timing differences are resolved to between four and six microseconds, a placement cue, and that the ear is a poor bass transducer with few hairs. Passion for Sound 2:40
• 2019-12-19Watts says the brain derives bass pitch from transients' higher harmonics; psychoacoustic tests removing transients make bass lines hard to follow and piano and trumpet hard to distinguish. Passion for Sound 5:28
• 2019-12-19Watts says transients matter for timbre, and that he learned this in the 1980s reading psychoacoustics textbooks at university, believing understanding hearing would make him a better designer. Passion for Sound 6:19
• 2020-01-02Watts says the brain resolves 4 microseconds, equivalent to 250 kHz, which bears on transient timing reconstruction, and that its timing accuracy is actually much finer than 4 microseconds. Passion for Sound 1:21
• 2020-01-02Watts says the 4 microsecond figure comes from neuron probes in anesthetized cats, but nobody knows how the brain separates instruments, which is a different matter. Passion for Sound 2:05
• 2020-01-02Watts says the needed timing accuracy cannot be stated, and cites Qutest, where switching between white/green and orange/red filters switches a 256FS WTA filter. Passion for Sound 2:54
• 2020-01-02Watts says his earlier three-stage IIR filter measured very like the WTA FIR stage, yet the change is audible, so even 88 nanosecond timing resolution matters. Passion for Sound 4:23
• 2020-01-02Watts says we perceive better than 1.3 microseconds, cannot yet set a required accuracy, and suspects any transient timing uncertainty, even 10 nanoseconds, is audible. Passion for Sound 5:03
• 2020-01-02Watts says modulation noise from saxophone and piano is spectrally identical, giving the brain four signals instead of two, merging the instruments and degrading separation and focus. Passion for Sound 8:51
• 2020-06-25Watts calls Mojo a mini DAVE anyone with a smartphone can afford, says a DAC wins if it makes you more emotional, and must make decoding easy for the brain. Part-Time Audiophile 8:26
• 2020-06-25Watts says separate instruments placed in a soundstage are an illusion created by the brain from ear data, and nobody knows how the brain separates sounds. Part-Time Audiophile 9:19
• 2020-06-25Watts says listeners can perceive a three-foot depth difference in a 60-foot concert hall with eyes shut, which no computer program can do. Part-Time Audiophile 10:04
• 2020-06-25Watts says making the brain's job easier makes music more emotional, while struggling to place instruments causes listening fatigue, so product errors must not interfere with brain processing. Part-Time Audiophile 10:50
• 2020-06-25Watts says PWM delay varies with signal level, modulating transient timing; the brain perceives 4 microsecond interaural delays; DAVE's interpolation filters originally ran to 16FS (768 kHz). Part-Time Audiophile 22:42
• 2020-06-25Watts says odd order harmonics sound worse because the ear generates second harmonic the brain compensates for, then recalls DAVE's three or four prototypes aimed at maximum linearity. Part-Time Audiophile 32:35
• 2020-06-25Watts says his son noticed the change unprompted; lower distortion improves clarity and detail, and assuming distortion below the ear's roughly -90 dB sine-wave limit is inaudible is dangerous. Part-Time Audiophile 35:33
• 2020-06-25Watts says distortion interferes with the brain's separation of sounds, sine-wave psychoacoustic tests give crude numbers, and describes an FPGA noise shaper producing distortion at 200 to 400 kHz. Part-Time Audiophile 36:29
• 2020-06-25Watts says fixing the 200 to 400 kHz noise shaper distortion was immediately audible, because very high order harmonics modulate transient timing, which can be perceived. Part-Time Audiophile 37:19
• 2020-06-25Watts says 200 kHz cannot be heard, but if it changes the timing of a transient it can be perceived because that effect is in-band. Part-Time Audiophile 38:02
• 2020-07-08Watts says the next ADC prototype PCB will be built in early autumn and muses that brain correlation may explain why depth depends on impossibly small signal accuracy. Head-Fi, Jul 2020
• 2021-01-02Watts says he dislikes DSP room correction because the brain compensates for room acoustics while DSP degrades imaging, depth, separation and timbre; he prefers acoustic room setup. Head-Fi, Jan 2021
• 2021-01-03Watts says the ear/brain responds to errors roughly as log(log), citing 164k to 1M taps and depth error steps, and ranks interpolation filter, DAC design and analog design. Head-Fi, Jan 2021
• 2021-02-01Watts says the cited result came from psychoacoustic testing where transients were removed and subjects compared steady-state piano or trumpet tones. Head-Fi, Feb 2021
• 2021-03-06Watts says the brain evolved to handle room acoustics but not noise floor modulation, aliasing and small-signal errors, and no commercial plans exist yet for speakers. Head-Fi, Mar 2021
• 2021-04-20Watts says he heard absolute polarity only on stacked Quad ESL57s, explains the ear's asymmetric nonlinearity, and offers to sign a unit at London CanJam. Head-Fi, Apr 2021
• 2022-01-31Watts defines noise floor modulation as noise rising with signal level, says the brain cannot separate it from the instruments, and says it makes the sound artificially bright. Darko.Audio 7:45
• 2022-01-31Watts says transients modulated by other instruments confuse the brain so it cannot separate instruments, and sums up the three factors that differentiate a Chord DAC. Darko.Audio 11:02
• 2022-02-12Watts says Mojo and Mojo 2 measure identically, but Mojo's warmth came from coupling-capacitor distortion removed by the DC servo; a bass shelf boost restores it. Head-Fi, Feb 2022
• 2022-03-19Watts says what we hear is the brain processing data from the ears, an illusion it constructs through processing we do not understand. MFG Audio Reviews 15:43
• 2022-03-19Watts says the brain perceives bass pitch, left-right location, timbre and note starts from transients, citing psychoacoustic tests where removing transients makes piano and trumpet indistinguishable. MFG Audio Reviews 16:12
• 2022-03-19Watts says the delays were 2 microseconds, 100 nanoseconds and under 10 nanoseconds, he chose the best unaware, and asks how the brain detects 100 nanoseconds at minus 201 dB. MFG Audio Reviews 33:04
• 2022-03-22Watts says the relationship is neither proportional nor logarithmic: a further tenfold error reduction still matters, tiny things need careful listening tests, and he wants bigger FPGAs. article, Mar 2022
• 2022-04-12Watts says the brain copes with harmonic distortion (cochlea about 4% THD) but not small signal distortion, noise floor modulation, anharmonic or timing errors, justifying -301dB accuracy. Head-Fi, Apr 2022
• 2022-04-26Watts says digital audio's primary problem is the timing of transients, defines a transient, and says the brain uses transient timing for lateral imaging and timbre. Audio Force 8:27
• 2022-04-26Watts says pitch, timbre variation, bass definition, instrument separation and focus depend on accurate transient timing, and timing errors confuse the brain and reduce emotional engagement. Audio Force 9:09
• 2022-08-19Watts says that while studying electronics and sampling theory he also studied the physiology of hearing and psychoacoustics, which showed him the importance of transients. AVstore 1:37
• 2022-08-19Watts says transient timing is crucial to perceiving pitch, timbre, location and separation, and digital's problem is reconstructing transients with correct timing, not information above 20 kHz. AVstore 2:28
• 2022-08-19Watts says correlating error levels from digital simulation with sound quality shows that very small errors that could never be measured are perceptible, showing how sensitive hearing is. AVstore 24:23
• 2022-08-19Watts says timbre perception depends on starting transients, citing tests where piano and trumpet are hard to identify without them, so transients modulated by other instruments degrade timbre. AVstore 32:29
• 2022-08-29Watts says filters make transient timing errors program dependent, which is why 100k and 1M taps sound different, that audibility does not fade with age, and that prototypes are delayed. Head-Fi, Aug 2022
• 2022-09-18Watts says his DACs make it easy for the brain to process the information; he analyzes how distortions and aberrations affect brain processing so you can enjoy music. The Source AV 26:54
• 2022-09-18Watts says you do not get listening fatigue. needs context The Source AV 27:24
• 2022-10-19Watts says the ear/brain images well despite degraded inputs, that headphone leakage misleads live monitoring, and that sealing the ears barely affects placement, depth or height perception. Head-Fi, Oct 2022
• 2023-01-28Watts says inter-aural delay resolution is about 10uS to 4uS raw, but a cited paper suggests population coding lets the brain resolve much smaller timing differences. Head-Fi, Jan 2023
• 2023-02-04Watts says noise that pumps with the signal cannot be separated by the brain from the instrument, so a saxophone with modulated noise sounds brighter. Dusty Audio 32:28
• 2023-02-04Watts says the brain detects the smallest errors, then introduces transient reconstruction as most important: digital audio is sampled, with about 22 microseconds between samples. Dusty Audio 35:26
• 2023-02-04Watts says psychoacoustic tests show that removing transients makes piano and trumpet hard to tell apart, so transients are used to perceive timbre. Dusty Audio 36:12
• 2023-02-04Watts says transients locate sounds through interaural delay; textbooks give about 4 microseconds resolution, but recent research shows no resolution limit. Dusty Audio 36:57
• 2023-02-04Watts says recent research shows the brain uses timing to virtually infinite resolution, so timing matters, and digital loses transient information between samples. Dusty Audio 37:40
• 2023-02-05Watts says R2R tops out at 16 times oversampling because FETs switch too slowly, causing high distortion; the ear is very sensitive to high-frequency distortion, even at 10 MHz. Soundnews 22:52
• 2023-02-05Watts says improving distortion at 10 MHz in the digital domain has a big subjective impact, down to aliasing and noise floor modulation, and he is working on transient accuracy. Soundnews 23:46
• 2023-03-04Watts says visual perception is a construct of the brain rather than the eyes' direct output, citing optical illusions that flip between perceptions. Head-Fi, Mar 2023
• 2023-03-26Watts recalls studying sampling theory and, on his own, psychoacoustics in the 1980s, learning that transient timing is perceptually vital for pitch, timbre and soundstage. Eric's Hi-Fi 41
• 2023-03-26Watts says most perceptual cues come from transient timing, which needs a sinc filter whose coefficients only converge on zero, so the filter must keep doubling for accuracy. Eric's Hi-Fi 1:26
• 2023-03-26Watts says textbooks give a 4 microsecond inter-aural timing resolution, but recent research shows the brain can detect almost zero time differences between the ears. Eric's Hi-Fi 6:09
• 2023-03-26Watts says his listening tests show the tiniest transient reconstruction error is audible, so reconstruction needs extreme accuracy, a harder problem than he expected in the 1980s. Eric's Hi-Fi 6:55
• 2023-03-28Watts says PWM's timing shift is a major transient reconstruction error that analog filtering cannot fix, and the brain uses transient timing for timbre, separation and bass pitch. The Headphone Show 32:01
• 2023-03-28Watts describes the common view that a DAC need only exceed the ear's performance, such as 1% distortion and 90-odd dB dynamic range. The Headphone Show 37:31
• 2023-03-28Watts says that view ignores how the brain processes sound; psychoacoustic tests examine only the ear, and audio chips are designed to specs rather than listening tests. The Headphone Show 37:51
• 2023-06-18Watts says nobody knows how the brain separates sounds into entities, and that he designs for performance without a budget, with Chord pricing the product from the bill of materials. Head-Fi, Jun 2023
• 2023-10-01Watts disagrees, recounting how he told a CanJam visitor that headphones he had heard for 30 seconds two months earlier now sounded different. The Source AV 18:44
• 2023-10-01Watts says ear coupling makes a huge difference, and that his memory caught something wrong from a 30-second listen months earlier. The Source AV 19:46
• 2024-01-27Watts says the claim that SRC is inaudible is wrong, advises sending bit-perfect data without SRC or upsampling to his DACs, and says transient timing is vital for perception. Head-Fi, Jan 2024
• 2024-03-20Watts says with saxophone and piano together noise floor modulation adds noise tracking each instrument plus a mixed product, confusing the brain's job of separating sounds into entities. MFG Audio Reviews 10:47
• 2024-03-20Watts says removing noise floor modulation keeps quiet instruments in focus, giving real transparency, and that it causes listening fatigue after about half an hour as the brain struggles. MFG Audio Reviews 14:45
• 2024-03-20Watts says he does not know how impossibly small errors are perceived, and guesses the brain uses an autocorrelation function that over long periods resolves infinitely small errors in noise. MFG Audio Reviews 16:30
• 2024-03-20Watts says passive components change sound, doubted mainly by people who never listen; errors well below the hearing threshold are audible because they interfere with the brain's processing. MFG Audio Reviews 41:15
• 2024-04-08Watts rebuts a claim that more taps make transients collide, saying longer sinc filters make transients independent, and each tap doubling improved sound. Head-Fi, Apr 2024
• 2024-05-16Watts attributes what the interviewer heard to transients: the brain, not the ears, uses transient timing to separate sounds into entities, place them in space and judge timbre. ConvinceMeAudio 4:54
• 2024-05-16Watts says without transients a piano and trumpet sound alike, the brain derives bass pitch from transients because the cochlea cannot, and CD samples are 22 microseconds apart. ConvinceMeAudio 5:36
• 2024-05-16Watts says limited taps make transients shift early or late depending on surrounding transients, so the brain loses separation, timbre, location and the starting and stopping of notes. ConvinceMeAudio 6:51
• 2024-05-16Watts says 16-bit is an arbitrary target; his research found even infinitely small timing errors are perceptible, which led him to improve the interpolation filter in Quartet. ConvinceMeAudio 8:31
• 2024-05-16Watts says reconstructed transients come slightly early or late, constantly shifting, which confuses the brain, since it uses transient timing for timbre, pitch, separation and placement. The Speaker Shack 1:10
• 2024-05-16Watts says we hear with the brain, not the ears; it creates the illusion, so ridiculously small errors matter, and science does not understand exactly how it does this. The Speaker Shack 8:00
• 2024-05-17Watts says reducing noise improves sound markedly, and that scaling is about transient timing, which the brain uses to separate instruments, perceive timbre and hear notes start and stop. AVstore 2:08
• 2024-05-17Watts says samples are taken 22 microseconds apart and transient timing between them must be reconstructed; otherwise transients arrive early or late, past and future ones disturb the present, confusing the brain. AVstore 2:57
• 2024-06-01Watts explains transients and localization, how crossfeed narrows headphone width, and ranks rectangular, triangular and pseudo-Gaussian dither below noise shaping, best for depth. Head-Fi, Jun 2024
• 2024-06-18Watts says the M Scaler is guaranteed better than a 16-bit reconstruction and Quartet better still, and explains how the brain uses transient timing for separation, location, timbre, note edges and bass pitch. article, Jun 2024
• 2024-06-18Watts explains how interpolation modulates transient timing, harming separation, timbre, bass and fatigue, says any timing error is perceptible, and lists Quartet's five FPGAs, 2,500 components, 75-ampere supply and two million code lines. article, Jun 2024
• 2024-06-26Watts says DSD256 has -20dB noise at 400kHz, all DSD rates show large modulator noise floor modulation, the brain perceives any timing change, and recordings stay limited to 192k. Head-Fi, Jun 2024
• 2024-07-12Watts says psychoacoustics is vital; studying electronics from 1979, he read psychoacoustics on his own because his halls of residence were next to the psychology library. HIFICLUB 3:28
• 2024-07-12Watts says what we hear is the brain's illusion built from ear data, and he studied its mechanisms to prepare for becoming an audio designer. HIFICLUB 4:16
• 2024-07-12Watts says music is transients, and the brain needs transients to perceive low-frequency pitch because the cochlea resolves low tones poorly. HIFICLUB 5:06
• 2024-07-12Watts cites studies where removing transients made double bass pitch impossible to follow and trumpet and piano hard to tell apart; transients also give tempo and note starts and stops. HIFICLUB 5:53
• 2024-07-12Watts says the brain uses transients and inter-aural timing to locate instruments in space and separate them into individual entities. HIFICLUB 6:40
• 2024-07-12Watts says the brain perceives errors below audibility thresholds; he had an engineer compare noise shapers at 180 dB and 200 dB distortion and noise at his home. HIFICLUB 23:24
• 2024-07-18Watts says 1M taps gave 16-bit accuracy but any timing error is perceptible, describes the isolated 75 ohm coax output, and says flight-ready Quartet needs better FPGAs. Head-Fi, Jul 2024
• 2024-08-01Watts introduces the interpolation filter's transient accuracy and says the brain uses transient timing to locate and separate instruments, recognize timbre, and hear notes start and stop. Audiophilesdoteu 3:53
• 2024-08-01Watts says transients also set low-frequency pitch; ordinary interpolation filters shift transient timing back and forth, degrading separation, timbre and soundstage, which FPGA power and his WTA filter improve. Audiophilesdoteu 4:40
• 2025-02-17Watts says the brain uses transient timing to separate sounds, judge timbre and location, perceive starting and stopping of notes, and calculate low-frequency pitch, which the ear resolves poorly. audio-2G 4:43
• 2025-02-17Watts says the brain calculates fundamental pitch from transient timing, and an interpolation filter degrades that timing because CD samples are 22 microseconds apart and reconstruction is never accurate enough. audio-2G 5:28
• 2025-05-12Watts says timbre perception depends on transients, citing psychoacoustic experiments where removing transients from trumpet and piano made the instruments hard to identify. Audiophile Junkie 1:24
• 2025-05-12Watts says the brain uses the interaural time delay to place sounds left to right within one degree, and also uses timing information to judge depth. Audiophile Junkie 1:56
• 2025-05-12Watts says timing helps the brain judge distance; textbooks gave a 4 to 6 microsecond interaural timing limit, but recent research shows the brain responds however small the difference. Audiophile Junkie 2:39
• 2025-05-12Watts says there is no resolution limit for timing differences the brain can respond to. Audiophile Junkie 3:24
• 2025-05-12Watts says digital audio's problem is transient timing: pitch, soundstage, timbre and note starts and stops come from transients, and the DAC must recover the waveform between CD samples. Audiophile Junkie 3:35
• 2025-09-14Watts says at very loud levels the ears go nonlinear and saturate, sounding brighter and more aggressive; with ear defenders things sound richer and smoother, as if distortion were removed. The Source AV 12:47
• 2025-09-14Watts says his ear defenders changed nothing but level at normal music levels, yet greatly changed sound at a loud band, showing it is the hearing, not the limiter. The Source AV 13:14
• 2026-03-17Watts says early digital sounded hard, bright, flat and not musical, blocking emotional involvement; he studied sampling theory and knew transient timing governs perceived timbre, pitch and location. ecoustics 1:16
• 2026-03-17Watts says a DAC must rebuild a continuous waveform with accurate transient timing, which improves timbre, separation, location and pitch, but the filters needed enormous processing impossible in the 1980s. ecoustics 2:18
• 2026-03-17Watts explains that an interpolation filter places a transient between samples slightly early or late, modulating back and forth and confusing location, timbre and pitch; he guessed 16-bit accuracy sufficed. ecoustics 4:05
• 2026-03-17Watts says the biggest DAC problem is reconstructing transient timing, which the brain uses for separation, timbre, bass pitch and depth; Quartet, six or seven years' work, launches next year. ecoustics 21:04
• 2026-03-17Watts says DSD sounds artificially soft and loses depth through poor small-signal accuracy, then begins explaining how finely the brain perceives depth, as with a phone moved half an inch. ecoustics 29:55
• 2026-03-17Watts says the brain locates sources from many cues, simplest the direct-to-reflected ratio; outdoors it uses the timing difference between the ground reflection and the direct sound. ecoustics 31:05
• 2026-03-17Watts says the brain also uses air absorption of high frequencies over distance, a loss at 20 kHz every fifteen meters, as a distance cue. ecoustics 31:53
• 2026-03-17Watts says the biggest depth cue is reverberant-to-direct energy from myriad ever-smaller reflections, so a DAC must reproduce very small signals from many sources very accurately. ecoustics 32:34
• 2026-03-17Watts suggests the brain may resolve depth by something like autocorrelation, and says we do not understand how it judges distance, nor can computers do it. ecoustics 43:20
• 2026-03-17Watts says a -301 dB error is perceivable, not audible; by measurements such as 0.007% headphone distortion and perfect DAC noise we should already have perfection. ecoustics 49:13
• 2026-03-17Watts says reproduction is still clearly unlike live music because people consider the ear, a poor transducer, rather than what the brain does with the information. ecoustics 49:59
• 2026-03-17Watts says what the brain does cannot be measured; it is a perceptual issue, not an audio one. ecoustics 50:43
• 2026-03-17Watts says for that the brain must be free of deciphering a mess of noises, which is where engineering comes in. ecoustics 1:27:07
• 2026-03-24Watts says the brain uses transient timing to locate instruments, judge timbre, separate instruments and perceive pitch, and the interpolation filter reconstructs the waveform from samples every 22 microseconds. Audio Force 11:37
• 2026-03-24Watts dislikes calling it more analog: it sounds like live unamplified music, because accurate transients let the brain understand music and engage emotionally, his main goal. Audio Force 16:45
• 2026-05-03Watts says the brain uses transient timing to locate instruments left to right, judge depth, form timbre and calculate low-frequency pitch, which the ear resolves poorly. Audio Force 6:04
• 2026-05-03Watts says the brain compensates for harmonic distortion the ear itself creates, but noise floor modulation is not harmonically related: 20 Hz to 20 kHz noise changes with signal, brightening instruments. Audio Force 12:18
• 2026-10-02Watts says a dog barking two miles away in a valley is located precisely in depth, yet on reproduced audio it is lucky to sound two feet behind the speakers. HiFi Buys 9:38
• 2026-10-02Watts says depth perception is complex, with early reflections signaling closeness, yet through open Velux windows behind his speakers he perceives a dog a mile away perfectly. HiFi Buys 10:48
• 2026-10-02Watts says that sound through point-source windows scattering in the room still conveys distance immediately, showing loudspeakers could do much better on depth. HiFi Buys 11:38
• 2026-10-02Watts says DAC64 had his first WTA interpolation filter, and at university he read 1950s physiology-of-hearing texts on interaural delay in the psychology library. HiFi Buys 17:01
• 2026-10-02Watts says transient timing was the key factor: interaural delay was once said to resolve 4 microseconds, recent papers find no limit, and the brain uses timing for bass. HiFi Buys 17:47
• 2026-10-02Watts says the brain uses transient timing to infer bass pitch, locate and separate instruments, and judge timbre; removing transients made a trumpet hard to tell from a piano. HiFi Buys 18:34
• 2026-10-02Watts says noisy, distorted 1930s mono recordings became enjoyable because the brain copes with natural analog distortion, as the ear itself is nonlinear, but not with digital's unnatural errors. HiFi Buys 26:02
• 2026-10-02Watts says interpolation filters make transients slightly early or late, modulated by past and future transients, and this blurring upsets the brain; this is where the WTA comes in. HiFi Buys 26:47
• 2026-10-02Watts says hearing is a construct the brain creates, separating instruments, placing them in space and perceiving timbre, which is why noise floor modulation matters. HiFi Buys 54:29
• 2026-10-02Watts says impossibly small numbers should not matter, but suspects the brain uses correlation, which can resolve infinitely small signals given enough time, to separate sounds. HiFi Buys 57:57
• 2026-10-02Watts says the ear acts as a dithered source, so unbelievably small errors change the signal's probability distribution and degrade the brain's ability to separate sounds. HiFi Buys 58:47
• 2026-10-02Watts says it is not; it is synthesized. needs context HiFi Buys 1:00:45
• 2026-10-02Watts says transient timing is one issue: with 768 kilohertz output, transients resolve to only 1.3 microseconds, yet recent biological papers suggest the brain has no limit to timing accuracy. HiFi Buys 1:14:27
• 2026-10-02Watts hypothesizes, not from textbooks, that the brain infers depth from the time difference between direct and reflected sound. HiFi Buys 1:25:41
• 2026-10-02Watts says a short direct-to-reflected delay implies a small room and closeness, a long one a big room and likely greater distance. HiFi Buys 1:26:30
• 2026-10-02Watts says this is profoundly disturbing and exciting because it overturns assumptions about what is perceivable and opens much to explore. HiFi Buys 1:31:01
• 2026-10-02Watts says the cochlear hair cells transmit pulses conveying frequency at a rate of only about 1 millisecond. HiFi Buys 1:31:45
• 2026-10-02Watts says thought of as a synchronous digital system, 1 millisecond would be slow. needs context HiFi Buys 1:32:01
• 2026-10-02Watts says the 1 millisecond cochlear pulses are asynchronous, so a nanosecond offset matters in how they transfer into the neuron structure, and the brain is not an analog system. HiFi Buys 1:32:13
• 2026-10-02Watts says the brain is an asynchronous digital system, unlike completely synchronous computers, and asynchrony has huge advantages because it can run at any speed. HiFi Buys 1:32:40
• 2026-10-02Watts says from a psychoacoustic standpoint transients are everything. HiFi Buys 1:59:24
• 2026-10-02Watts says 'hearing' implies the ear. needs context HiFi Buys 1:59:37
• 2026-10-02Watts says perception has nothing to do with the ear; the brain reconstructs an incredibly accurate audible illusion that we take as reality. HiFi Buys 1:59:39
• 2026-10-02Watts says he has noticed that about one second before he falls asleep, depth collapses. HiFi Buys 2:00:13
• 2026-10-11Watts says aliasing errors are not harmonically related to the signal, confuse the brain's pitch tracking and degrade transient timing; Quartet eliminates aliasing unlike standard pro ADCs. Distorsiuni Interioare 13:35
• 2026-10-14Watts describes a piano hammer's burst of white noise turning into string vibration as part of the transient, saying much timbre comes from transients, which are psychoacoustically essential. Part-Time Audiophile 17:02
• 2026-10-14Watts says conventional engineers equate hearing with ear performance, assuming distortion and noise below audibility thresholds give perfect sound, which today's chains achieve. Part-Time Audiophile 17:52
• 2026-10-14Watts says systems below audibility thresholds still sound unlike live music because the brain, not the ear, separates sounds into entities, locates them in 3D and computes timbre. Part-Time Audiophile 18:37
• 2026-10-14Watts says the brain relies on transient timing for low-frequency pitch, left-right and depth location, timbre, and telling whether one or two instruments are playing. Part-Time Audiophile 19:23
• 2026-10-14Watts says degraded transient timing makes timbre, pitch, location and separation hard to perceive, causing listening fatigue and making emotional engagement harder. Part-Time Audiophile 20:12
• 2026-10-14Watts says when the brain need not work hard it follows the music easily, which makes emotional engagement easier. Part-Time Audiophile 21:04