The Intricate Relationship Between Wave Properties, Loudness, and Pitch
The perception of sound is a complex process involving the interplay of wave properties, loudness, and pitch. Our brains interpret these elements to create a rich auditory experience. This article delves into the fascinating relationship between these components and explores how our brains process and perceive sound.
A visual representation of a sine wave, illustrating amplitude and frequency.
Understanding Loudness and Frequency Perception
Let's focus on the low frequencies below mid-range, say 20-500 Hz. The truth is that at low overall volume, lower frequencies have lower perceived loudness than they have at normal listening levels (due to lower sensitivity in the physics of the inner ear). At these low listening levels, lower frequency causes lower loudness in a sense.
Consider the "Loudness Contour" feature on "Hi-Fi" stereo amplifiers, designed to boost bass and treble at quiet listening levels to compensate for the ear's reduced sensitivity to these frequencies. So now when you hear some music go quieter, your brain tries to "boost" your perception of the highs and lows, so you don't miss out on what you're listening to. But what if your brain gets mixed up on cause and effect?
But your brain may think that so some extent lower loudness also causes lower frequency. All it "knows" is that there is a correlation between lower frequency and lower loudness. So now when you adjust the amplitude of a low note, your brain may expect the frequency to change with it, and when it doesn't change as expected, your brain perceives an "unexpected" shift in frequency that isn't really there in the physics. So as a low note is brought up in amplitude (physics), your brain expects the frequency to go up too.
Auditory Illusions and Brain Perception
I wonder if this could be the result of a logical fallacy (affirming the antecedent) happening in your brain, at the level of instinct.
By the way, those hairs have exotic physics happening in them: hairs in water should be highly damped, yet they ring like little bells. That is because they have positive feedback with muscle molecules built-in that compensate for the damping of water and keratin so that they vibrate more like steel in air than hair in water. Freeman Dyson talks about research he did with Tommy Gold on this at one time.
Schematic diagram of the human ear showing the outer ear, the middle ear, and the inner.
Testing the Theory
But what I've written here could be tested simply: Have a subject listen to different notes and adjust the volume himself to make them all the same loudness. Then have him do the same as you vary one note in volume: have him adjust the pitch so that it is the same pitch to him. Then try to teach his brain the opposite loudness compensation: play full spectrum music softer and louder, while over-compensating the highs and lows, and then run the tests again to see if the results are affected.
Retraining Musical Perception
As far as re-training your musical perception goes - I have been able to re-learn harmonic relationships by listening to music that I have shifted (not scaled) in frequency, which initially sounds like banging on trash cans, but over time (several minutes) begins to sound musical again, harmonic. Then listening to the original music sounds initially like trash cans again, but gradually improves back to natural sound perception.
Here's a table summarizing the relationship between frequency, loudness, and perceived pitch:
| Wave Property | Perception | Description |
|---|---|---|
| Frequency | Pitch | The rate at which a sound wave repeats, measured in Hertz (Hz). Higher frequency corresponds to higher pitch. |
| Amplitude | Loudness | The intensity or power of a sound wave, measured in decibels (dB). Higher amplitude corresponds to greater loudness. |
| Waveform | Timbre | The shape of the sound wave, which contributes to the unique quality or "color" of a sound. |