A fuller sound.
Infrasound below 20 Hz and ultrasonic components above 20 kHz are perceived in different ways. Both extend beyond what we describe simply as audible sound.
Infrasound and ultrasound
The technology behind the sound.
The spectrum of musical instruments does not end at the range we usually call audible. We ask what this means for the experience of music and for the design of audio equipment.
The right kind of distortion can enrich music.
Imagine all the world’s music confined to a narrow band of frequencies. In reality, instruments such as a violin, cymbal or oboe produce measurable harmonics above the audible range. We do not hear these directly as pitch, but their presence and interactions may still be part of the whole musical event.
“Though this be madness, yet there is method in’t.”
W. Shakespeare · Hamlet
Brain responses.
Some studies have explored whether components above the audible range may be associated with changes in brain activity and in how natural music feels.
A closer connection.
Music is more than the conscious perception of pitch. Space, dynamics and physical sensation may also shape how close we feel to a performance.
What we can sense but cannot directly hear.
Research has not reached a consensus on every question. We therefore treat possible effects as phenomena to measure and investigate further, rather than as established facts.
Infrasound and ultrasound.
Our ears do not perceive frequencies above 20 kHz directly as pitch. Yet ultrasonic components from instruments can be measured, so they may be relevant when examining the complete signal chain.
Petrosino & Canalis · research referenceIntermodulation.
In a non-linear system, two high-frequency components can produce a difference frequency in the audible range. Components at 30 and 35 kHz, for example, may interact to create a 5 kHz component.
Fastl & Zwicker · PsychoacousticsThe body senses sound, too.
We experience sound below 20 Hz partly as physical sensation. Possible physiological and neurological effects of higher ultrasonic frequencies have also been studied, but their interpretation remains debated.
Kuribayashi et al. · 2017 Oohashi et al. · 2000What does this mean for our design?
In many high-end systems, these effects arise from how the entire signal path behaves. We also consider components outside the audible range deliberately. The goal remains the same: less sound of the equipment, more of the music.
For us, natural distortion is not colouration for its own sake. It is a way to preserve more of the complexity of a musical event.
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