I just returned from an Alaskan cruise. Much to my disappointment there was no penguin fishing and I never did see an Atlantic salmon, but other than these two let-downs, it was a great trip. We visited Juneau, Skagway, and Ketchikan. “Ketchikan” is a Northwest First Nation word meaning “many-jewellery-shops-for-tourists-near-the-cruise-terminal”.
It occurred to me during the trip when I was watching a glacier calve- a section of the ice breaking off and falling into the ocean- that glacier calving is very much like speech. I am sure that everyone else on the cruise felt the same way.
When a sheet of ice falls off of a glacier, you first hear the high-frequency cracking as the ice breaks free, and then a moment later, you hear the low-frequency rumbling as it crashes into the sea (and hopefully not onto the ship). This is a linear progression- first one sound, then another. There is never a point when the two sounds coincide. The low-frequency sounds are never simultaneous with the high-frequency sounds.
Well, this is identical to speech (in quiet). We hear the lower-frequency sonorants (vowels, nasals, and liquids), and then in a different time period (a moment later) we hear the higher-frequency obstruents (affricates, fricatives, and stop consonants).
The auditory input of hearing a glacier calve is similar to that of conversational speech.
When it comes to music, this is characterized by simultaneous occurrence of sound, much like speech in noise. In music, this is called harmony.
Now let’s combine glaciers and in-ear monitors for musicians. Although there is no definite research on this issue, in-ear monitor manufacturers market their devices based on the number of receivers. A single receiver device (like most hearing aids) sells for less than one with more receivers. There is an underlying assumption that more is better (or at least more expensive) than fewer. This doesn’t seem to be the case with hearing aids, however.
It is assumed that a multi-receiver device (such as most modern in-ear monitors for musicians) can route the transduction of high-frequency music energy through a different mechanism from the low-frequency transduction of music energy. After all, a receiver whose diaphragm is waggling quickly for high-frequency sounds, can’t be as efficient as if it were waggling slowly for the lower-frequency sounds. This seems to be the intuitively obvious reason for going with more receivers. It is especially obvious for music where low-frequency bass notes occur simultaneously with the higher-frequency treble and harmonic notes.
Having said this, I have been unable to locate any research that demonstrates that this assumption is valid. If indeed there is some validity to this assumption, then the effect would be greater for music than for speech. Speech in quiet, never has low- and high-frequency components simultaneously, yet music does.
This is an experiment that needs doing. Not only would it provide support (if the assumption is true) that more is better than fewer (at least for music), but there may be some data supporting the contention that even for hearing aids (especially for speech in noise) more than one receiver may be the way to go. Or perhaps not, if indeed, more is not shown to be better than fewer.
Just a thought and a possible future experiment to be done. What a neat thing to do for a Capstone project!