Psychoacoustics
Psychoacoustics studies the relationship between physical sound and what listeners perceive. Your ears and brain separate frequencies, compare timing and level, fill in missing information and discard parts of a sound that stronger neighbors hide.
- sound is measured
- hearing is interpreted
- context changes perception
Where you run into this
- Mixing
- Arrangement
- Speaker design
- Hearing science
Why are your ears not a level meter?
The ear is not equally sensitive at every frequency. At moderate levels, hearing is especially sensitive through much of the midrange and less sensitive at very low and very high frequencies.
Equal-loudness contours show how much sound pressure different frequencies need to seem equally loud. Their shape changes with level, so a mix heard quietly often seems to lose bass and extreme treble before its midrange disappears.
What is auditory masking?
Masking happens when one sound raises the hearing threshold for another. It is strongest when the sounds are close in frequency, although a broad or very loud masker can cover a wider region.
A bass guitar and kick drum can both be present on a meter while one is hard to hear. Turning either one up may increase level without restoring clarity. Changing timing, register, arrangement or spectrum can separate them more effectively.
Three ways sound can be hidden
- Frequency masking
Simultaneous energy in nearby frequency regions makes the quieter component harder to detect.
- Temporal masking
A strong sound can briefly reduce sensitivity to a sound just before or after it. The effect is usually stronger after the masker.
- Informational masking
Play two similar vocal lines together and try to follow only one. Even with enough physical separation, attention and grouping can become the bottleneck.
Why does a missing fundamental still have pitch?
If a sound contains components at 200, 300, 400 and 500 Hz, the spacing suggests a 100 Hz fundamental even when 100 Hz itself is absent. The auditory system can infer that pitch from the pattern.
This is why a small speaker can suggest bass notes below its strongest output range. It reproduces enough upper harmonics for the listener to reconstruct the pitch.
How do you locate a sound?
Play a low tone from one side and the brain relies strongly on its tiny arrival-time difference between the ears. With a high tone, the head creates a clearer level difference by shadowing the far ear. The outer ear adds direction-dependent filtering for front, back and height.
Room reflections complicate these cues. The first arriving wave often has the strongest influence on perceived direction, while later reflections add width and distance.
Measurement and perception are not interchangeable
| Physical description | Perceptual result | Why they can differ |
|---|---|---|
| frequency in Hz | pitch | spectrum and context affect the inferred note |
| sound pressure level | loudness | frequency, duration and adaptation matter |
| spectrum | timbre | attack, decay and grouping also shape identity |
| channel balance | position | timing, room cues and head movement contribute |
Run a masking check on a mix
- Choose the hidden partname the instrument or detail you cannot follow.
- Listen in soloconfirm that the sound itself is clear.
- Add likely maskersbring tracks back one at a time.
- Change arrangement firsttry octave, rhythm or note length before boosting.
- Check quietlyconfirm that the important line survives at a lower level.
Protect the listener you rely on
Hearing adapts, so a loud session can make a bright mix seem normal and reduce your ability to judge small changes. Take quiet breaks and compare at moderate monitoring levels. Persistent ringing, pain or sudden hearing change needs professional attention.