How do we listen?

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B. Absolute Phase Audibility (or Lack Thereof)​

Absolute phase (or polarity) refers to the initial direction of pressure change in a waveform.12 As mentioned previously, the question of whether humans can detect an inversion of absolute polarity for complex sounds like music in typical listening environments remains contentious. Early research suggested insensitivity.49 Some studies using specific, often asymmetrical, artificial signals (like single-cycle transients or specially constructed waveforms) under controlled conditions (headphones, anechoic chambers) have demonstrated statistically significant detection of polarity inversion.

 

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C. Relative Phase Sensitivity and Just Noticeable Differences (JNDs)​

The auditory system is sensitive to relative phase differences between frequency components, particularly when these differences alter the signal's temporal envelope or fine structure.17 Experiments using harmonic complex tones have shown that changing the phase relationships between harmonics, even while keeping the magnitude spectrum constant, can result in perceptible changes in timbre.59 For instance, aligning harmonics in cosine phase versus sine phase, or alternating phases, can produce different waveform shapes and potentially different neural firing patterns, leading to audible differences.59

The Just Noticeable Difference (JND) for phase changes, however, is not a single value. It depends strongly on the specific signal characteristics (e.g., fundamental frequency, harmonic content, presence of transients), the frequency range being considered, the magnitude and nature of the phase alteration, and the listening conditions.59 Furthermore, masking effects are highly relevant: phase shifts that might be detectable in a simple, isolated tone can be rendered inaudible (masked) by the presence of other frequency components in a complex sound like music.55

 

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D. Frequency Dependence of Phase Perception​

Sensitivity to phase effects varies significantly across the frequency spectrum:

• Low Frequencies (< 1.5 kHz): In this range, the auditory system exhibits exquisite sensitivity to interaural phase differences (IPDs), which arise from interaural time differences (ITDs) and are a primary cue for sound localization.54 Sensitivity to ITDs can be as fine as 10 microseconds.49 Some studies suggest monaural perception of phase-induced timbre changes is also more pronounced at lower fundamental frequencies.59 Sensitivity to group delay (in ms) might be lower at very low frequencies, meaning larger delays are required for detection.17
• Mid Frequencies (approx. 500 Hz - 5 kHz): This region is critical for speech intelligibility and musical timbre. Research has shown that phase distortions in the midrange can be audible, particularly with specific test signals or under headphone listening conditions.13 The ear's sensitivity to waveform shape changes caused by phase shifts seems relevant here.
• High Frequencies (> 5-8 kHz): Sensitivity to phase information generally decreases at higher frequencies. The ability of auditory nerve fibers to precisely "phase-lock" to the fine structure of the waveform diminishes above roughly 4-5 kHz.68 While localization cues shift to interaural level differences (ILDs) at high frequencies 58, the ability to perceive monaural phase effects related to waveform shape also appears to decline significantly.59 Phase shifts above 10 kHz are widely considered inaudible.69

 

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Room Acoustics: In typical listening rooms, sound reaches the listener not only directly from the loudspeaker but also via multiple reflections off walls, floor, ceiling, and furniture. These reflections travel longer paths, arriving delayed relative to the direct sound.1 This creates complex, position-dependent interference patterns (comb filtering) and introduces substantial phase shifts that often dwarf those originating from the loudspeaker itself.1 This "room distortion" acts as a powerful masker, making it much harder to perceive the potentially more subtle phase non-linearities of the loudspeaker.13 Consequently, phase effects clearly audible under anechoic conditions or via headphones often become inaudible in a normal reverberant room.

 

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And the counter video

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It is the brain that hears, not the ears; the ears are merely the instruments the brain uses to interpret what we "hear." Once the speakers have "broken in," the brain also adapts.

 

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Interesting tidbit…

On a slightly different note, I once asked several binaural researchers in Korea, hearing‑aid manufacturers, and local doctors, “What happens if you lose hearing entirely in one ear or your ear is completely damaged?”

Their common response was that your brain compensates to some extent because your past listening experiences are imprinted in it. Of course, precise localization is diminished compared to having two working ears, but the brain “imagines” the imaging based on the data it already has, so a sense of spatial image is still maintained.

Of course, if the memories of listening with two ears fade and disappear, that compensatory ability is lost. The time frame varies by person—it can be as short as a few weeks or months, or it can stretch to several years or even decades.

 

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A "warm" sound in audio generally refers to a tonal quality that is smooth, rich, and pleasant, often associated with analog equipment or certain types of speakers and headphones. In terms of amplitude (frequency) response, "warmth" typically translates to:

1. Slightly Elevated Low-Mid Frequencies (around 100–500 Hz)​

• This range includes the body and fullness of most instruments and vocals.
• Boosting this region slightly can give the sound more richness and roundness.

2. Rolled-off High Frequencies (above 10 kHz)​

• A warm sound often has less emphasis on the very high frequencies, which can make it sound smoother and less harsh.
• This avoids overly bright or brittle tones.

3. Moderated Upper-Midrange (2–5 kHz)​

• Reducing the upper mids slightly can reduce harshness or sibilance, contributing to a more relaxed and cozy sound.

 

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Here's a typical dB range associated with creating a "warm" sound in terms of amplitude (frequency) response. These are approximate values used in mixing, mastering, or speaker tuning:

1. Low-Mid Boost (100–500 Hz):​

• +1 to +3 dB boost
• Adds body and warmth to vocals and instruments
• Avoid boosting too much to prevent muddiness

2. Upper Midrange Control (2–5 kHz):​

• 0 to –2 dB dip
• Reduces harshness or brittleness, particularly in vocals and cymbals
• Often done with a gentle, wide Q (low resonance)

3. High-Frequency Roll-Off (10 kHz and above):​

• –1 to –4 dB cut
• Smooths out excessive brightness or sibilance
• Can mimic analog tape or tube gear warmth

 

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Quote from the grandmaster audio researcher ....

Listeners in the Harman tests are audiometrically tested, and then trained to recognize and describe common flaws in sound quality. The descriptions are important feedback to the design engineers.

My hearing thresholds were still better than average for my age, but years of use and abuse had taken their toll. I smile when I read grey-beard reviewers waxing eloquent over audio components. I wonder what they really sound like - and I may never be able to truly tell either.

Life is like that ...
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Siemens Digital Industries Software Community

Masking is an auditory phenomenon in which one sound alters the perception of another sound, sometimes making that other sound inaudible.
There are two forms of masking: spectral masking and temporal masking.

 

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Related to localization / imaging ...

clip1.mp4

drive.google.com

 

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Your brain can "tune out the room reflections". That is why your HiFi system sounds good -- "you don't hear the 5 copies of the original sound".

clip3.mp4

drive.google.com

Meanwhile the recorded version of your HiFi in the same room sounds echoey ...

Try it!
Record your HiFi system playing on your phone, then play the recording back, sounds echoey doesn't it?
How come your ears don't hear the echo?

 

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Your eyes affect how you listen!

clip5.mp4

drive.google.com

I wonder if those setups where speakers are pulled far into the room, with the eyes seeing all that space behind the speakers, somehow tricks the brain into imagining more depth? Hmm...

 

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Just in case you want to watch the entire 2hr interview ... they even talk about how to hypnotize chickens

 

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My takeaway from watching the video:

• larger room can contribute to better sound quality
  • reflections happen further away (takes more time, helps the brain separate direct vs. reflected)
  • reflected SPL is lower when it reaches back at the head
• speaker with well controlled directivity can contribute to better sound quality
  • reflected frequency content is similar to the direct frequency content

Why Worry About Room Acoustics?

1. Want to achieve truly amazing immersive audio performance? You must understand that at least half of the quality depends on your room’s acoustical thumbpr...

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