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Perceived pitch and loudness interact: intensity shifts perceived pitch and sensitivity varies with frequency

Concept L2First instrument B · Sound design & synthesis

Equal-loudness contours (Fletcher-Munson / ISO 226:2003) show that the ear’s sensitivity to amplitude is not flat across frequency: at low frequencies much more sound pressure is needed to produce the same perceived loudness as a midrange sound. Intensity also affects perceived pitch: above 2000 Hz, increasing intensity while holding frequency fixed raises perceived pitch; below 1000 Hz, increasing intensity lowers perceived pitch. These psychoacoustic interactions matter for sound design: a heavily boosted bass sound at low volume may vanish in the mix, and the apparent pitch of a synthesized tone can shift when the volume is changed.

Examples

The 60-phon isophonic curve requires more dB at 100 Hz than at 1000 Hz for the same apparent loudness. A bass synth patch may need amplitude compensation when the output level changes.

Assessment

Explain why a synthesized bass note at 80 Hz that sounds balanced at high volume may sound thin at low volume, and what countermeasure a sound designer could apply.

Prerequisites — understand these first

Don't confuse with

Sources

“the intensity of a sound influences the perception of its pitch. Without going into too many details, it suffices to note that above 2,000 Hz, if we increase the intensity of a sound while maintaining fixed frequency, we will perceive that the pitch is rising”
corpus · electronic-music-and-sound-design-vol-1-cipriani-and-giri-of · chunk 9

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