Small speakers exploit the residue pitch effect to create low-pitch sensations

Evidence

Small speakers in a laptop are very poor at creating low-frequency sound. If an object producing the sound is much smaller than the typical wavelengths of the sound produced, the pressure (force) and the acceleration at the surface of the object are nearly in phase, as explained in section 7.11. Once the object is appreciable in size compared to the wavelength, it is possible for the force and velocity to be more nearly in phase, greatly enhancing the work done on the air by the vibrating object, and therefore its loudness. Small laptop speakers can produce only a very weak tone if driven sinusoidally at 100 Hz (wavelength about 3.5 meters, much larger than the speakers). However, because of the residue pitch effect, the same speaker producing a 100 Hz complex tone gives rise to the strong sensation of a 100 Hz pitch, in spite of the near total absence of a 100 Hz partial, and a very weak 200 Hz partial. — Eric J. Heller, Why You Hear What You Hear- An…, 2071

Categorization

• CANDY: A genuinely fun, tweetable fact: laptop speakers produce bass pitches that aren’t physically there.
• XREF: Connects the physics of sound radiation to psychoacoustics — a mechanism connecting transducer size, wavelength, and perceived pitch.