Adding distortion to a sine-wave sub-bass makes it audible on small speakers

A pure sine wave sub-bass produces very low frequencies that small speakers (phones, laptops) cannot reproduce. Adding distortion to the sine wave generates harmonic overtones in the mid-bass range that small speakers can play. The listener hears these harmonics as a sense of bass weight even when the fundamental is inaudible. This is a practical translation technique in genres like grime and electronic music where sub-bass is structurally important but the audience may listen on consumer devices. The distortion also adds energy and character that can suit aggressive genres.

Examples

Sine wave at 50 Hz played on phone: nearly inaudible. Same sine with light to moderate distortion: audible ‘bounce’ due to 100 Hz, 150 Hz harmonics. Common tools: a soft-clip distortion or saturation plugin inserted after the sine oscillator.

Assessment

Explain why a pure sine-wave sub-bass sounds weak on a laptop speaker while a distorted version of the same sine sounds present. What frequency content does distortion add, and how does the listener perceive it?