Otoplastics reduce by 25, 15 or 9 dB. Not convenient to listen to a music performance. Is there something that lets the sound through to eg 80dB and what goes above that doesn’t pass?
Answer
Dear Willy,
No, that doesn’t exist.
Two parameters are important for sound: loudness and frequency.
The loudness is expressed in a level. Usually one speaks of a sound pressure level: that is a measure of the sound intensity at a certain point, eg at the height of your ears. You can reduce levels in value by, for example, using an otoplastic or other hearing protection or simply moving further away from the sound source or in another room. However, the levels are all reduced regardless of their strength. For example, if the sound attenuation is 20 dB, 120 dB becomes 100 dB, 80 dB becomes 60 dB, and 40 dB becomes 20 dB. And 10 dB becomes -10 dB, because negative sound pressure levels also exist.
A decrease of 20 dB sound pressure level corresponds to a decrease in sound pressure (in Pascal) by a factor of 10. The above examples are repeated 20 Pascal 2 Pascal, 0.2 Pascal becomes 0.02 Pascal, 0.002 Pascal becomes 0.0002 Pascal and becomes 0.000063 Pascals 0.0000063 Pascals. Nothing to do.
However, the frequency can be selectively reduced: this is referred to as a filter. For example, a wall is a filter that allows the low tones to pass through better than the high tones. Standing further away from something also amounts to applying a filter because high tones are again dampened more strongly than low tones: at a great distance from a music festival you first hear the bass, only closer do you hear voices. A filter also exists purely electronically (digital): for example, on data transmission of any kind (such as telephone conversations) filters are applied that only allow the most important frequencies to pass in order to save bandwidth. That “band” of bandwidth, by the way, refers to frequency “bands”.
It is therefore perfectly possible to filter only the high tones and not the bass tones. Conversely, it is a lot more difficult (or even impossible) because of the physical phenomenon that low tones are always harder to mute. The cause is the long wavelength associated with low frequencies.
But mute loud tones and less loud not is impossible: so I’m afraid you have to put your idea away. In any case, the smartest thing you can do is to be very careful with your hearing. Hearing damage can be permanent.
Kind regards,
Pieter Schevenels
Answered by
dr. ir. Pieter Schevenels
sound acoustics engineering
Agoralaan University Campus Building D BE-3590 Diepenbeek
http://www.uhasselt.be/
.