Question

On recent audio show, I have noted down 5 rooms where sound was the best to my ears, so I can make second round to hear them again. After few days, when analysing speakers used in these 5 rooms, all of the speakers were capable of reproducing music over hearable human range, sometimes to 50 kHz. One explanation is that these super tweeters are only doing better job inside hearable range, and my question is: If superposition of many ultrasound waves (usualy overharmonics on every instrument) can lead to wave shape which is hearable? We know that discrette ultrasound pitches cannot be heard. So, we are hearing then influence of unhearable pitches? Thank you! Silvio

Answer 1

The improved audio quality in rooms with speakers capable of emitting ultrasound is likely due to high engineering quality of the speakers rather than a direct influence of ultrasonic frequencies on audible sound since speakers are generally not designed to generate significant levels of intermodulation distortion that would turn ultrasonic frequencies into audible sounds.

Step-by-step explanation:

The question refers to whether the superposition of many ultrasonic waves can lead to a waveform that falls within the hearable range for humans. The normal range of human hearing is from 20 Hz to 20 kHz, with any sound above this range being classified as ultrasound. While discrete ultrasonic frequencies are not audible, the nonlinear interaction of ultrasonic waves can generate audible components through a process known as intermodulation distortion. For example, if two ultrasonic waves at different frequencies interact, they can produce sum and difference frequencies, some of which might fall within the audible range and would be heard as a result of their interaction.

However, typical speaker systems are not designed to generate significant levels of intermodulation distortion, so the perception of improved sound quality in the rooms you visited likely doesn't come solely from the contribution of ultrasonic frequencies. It is more plausible that speakers with super tweeters that can emit ultrasound also have a high level of engineering quality that allows for better performance within the audible range, rather than the ultrasonic waves directly influencing what is heard.

Additionally, the materials and design of a speaker that can accurately reproduce ultrasonic frequencies might also improve the fidelity of the audible frequencies due to better transient response or reduced distortion in the audible range. Therefore, while the influence of unhearable pitches (ultrasonic frequencies) on audible sounds can occur, it is typically not a significant factor in high-fidelity audio reproduction.