> transient high end frequencies. My hypothesis is that the presence of frequencies outside of the range of our ears affect the frequencies within our hearing r

> transient high end frequencies. My hypothesis is that the presence of frequencies outside of the range of our ears affect the frequencies within our hearing range This is something I wonder about, too, but by my limited knowledge of signal processing the low pass effects of the signal transmission path do simply not admit any such frequencies. I wonder whether that counts for all orders of derivation, though. I wonder if higher frequencies can cause resonance in lower frequencies, undertones instead of overtones so to speak, maybe in exotic geometries like the inner ear. Echo location famously works better in the ultrasonic range and involves higher order derivatives. We don't talk of constant sinusoids, but ultrasonic sweeps and chirps (not sparkle :D). We can't hear ultrasound, but perhaps we can sense it similarly to how we can sense lowest frequencies as rumble. I really don't know the maths, what is a really low frequency note played for nanoseconds? High frequency Pulse Width Modulation is used to modulate sound in the audible range, which is quite tricky to get right mathematically and in hardware. The common problem is the introduction of ringing, indeed. By the way, I really like to listen to music under the shower in the next room. I hear, or rather hallucinate, the most wonderful sounds under the noise.