Delving deeper: the sound of silence

Another, nice illusion! But also a slightly over- / misinterpreted one ...

In general, creating an illusion is tweaking the perceptive system. This goes for any perception. Such as the perception of an event or a person or a healing process by working with conditioning and suggestive methods. And also for the perception of optical inputs and in this case for acoustical events by fooling your perception by specific signals.

In this specific experiment, the time resolution of the acoustical system gets specifically fooled. This experiment does not trade with a sequence of test tones, but instead with a sequence of zero-spl periods. So, instead of a sound, logically the silent periods gets awkwardly misinterpreted in terms of their durations. This is quite evident, and it has nothing to do wheter you can hear silence or not: It's not an experiment about the quality of acoustical stimuli, it's an experiment about time durations interpretation.

One can't hear silence. Like one can't see absence of light. Where there is no stimulus, there is nothing to decode. But then, there is still a lot to misinterprete by the specific, ongoingly working perceptive system. And "nothing" is not very familiar and can even become psychologically alarming. Therefore, a neat illusion may provide some cosy comfort.

And also, within absolute silent surrounding you subjectivly still are not in a silent world: There has been experiments with people inside of acoustically isolated anechoic chambers. After some time, these test persons perceived the sounds of theirs body, such as blood streaming turbulences inside of your carotis and the like. And some freaked out because of loosing the acoustical reference to theirs acoustically familiar outside world.

As this experiment is playing more with time perception than with acoustics, let's also mention that it is well known that time is not representated as an own psychophysiological quality. Therefore it is relatively easy to blur a therefore un-referenced perception of time. Short term, as in this experiment. And also longer term: Just make another experiment and project yourself into a lonesome four weeks desert journey. No calendar, no smartphone, no radio. And after ten days, it will no more be obvious wheter it's thursday or friday today. Wrong. It was already saturday. And you also had the impression, that day before yesterday was a very short day, whereas today lasts forever?

And hey ... what is silence? Silence in a technical term is 0dB. And silence in a subjective term .. what's that? You will never expercience yourself in absolute "silence" while you are alive. Neither outside silence, nor inside silence. If you want real, total silence, then you first will have to die. Which will then cause another problem with a dysfunctional perceptive system. You won't be able to hear this silence any longer.

Finally, I have the pleasure to point to a very specific sound of silence, which was one of my favourites in my very romantic days:

 
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Reading the first lines of this link ...

... “Our approach was to ask whether our brains treat silences the way they treat sound," study author Chaz Firestone said in a news release on Monday ...

This seems scientifically ok.

... "you can get the same illusions with silences as you get with sounds, ..."

This finding seems also scientifically ok.

... If you can get the same illusions with silences as you get with sounds, then that may be evidence that we literally hear silence after all ...

This is no more science, it's plain BS instead. It's a statement for journalists, something primarly aimed to sensationally sell and hype his research. It's meant for headlines, and it works very wel. The headline of this link is:

The illusion of silence: Why researchers say you can hear the sound of nothing


This is certainly what the scientist intended. And he was clever in doing so, and evidently scientifically not literally to blame, after all. Because he said ...

... If you can get the same illusions with silences as you get with sounds, then that may be evidence that we literally hear silence after all ...

He wisely did not say

... If you can get the same illusions with silences as you get with sounds, then that is the proof that we hear silence. ...

And the more we discuss this topic here, the more we will follow the intention of the clever and hype-hungry scientist.
 
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To say that we 'hear' silence is scientifically disingenuous and technically incorrect. I would be ok with the experiment if the word 'sense' (or similar) was substituted. The visual analogy of this is the 'stopped clock' illusion, known as chronostasis, a temporal illusion.
 
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This is a natural result of the characteristics of the human ear. To perceive silence, it takes approximately 0.1 seconds for the brain to register it. Even if there is a 0.2-second silence, the perceived duration is around 0.1 seconds. When a sound is heard during that silence, it takes a little time to recognize the silence again, even if it may not require the full 0.1 seconds. As a result, the silence feels shorter.

The same applies when analyzing with FFT (Fast Fourier Transform). With a sampling rate of 96kHz, a length of around 8192 corresponds to approximately 0.1 seconds. If the length is longer than this, it becomes less relevant to the human ear. When turning a sine wave on and off every 0.1 seconds, the on-and-off transitions can be perceived by the human ear. However, if you use an 8k FFT, there is hardly any silence between the transitions. With a 16k FFT, detecting the silence becomes impossible. A suitable length is necessary to be compatible with the human ear.
 
MarcelvdG - Good time resolution is possible only at high frequencies. The original article is waiting for silence, which means that low frequencies (=poor time resolution) must die down too.
Ed

Actually, I didn't bother to read the article as the abstract already didn't make much sense to me.

Still, claiming that the mammalian auditory system is a spectrum analyser is an oversimplification. For example, the basilar membrane with the hair cells acts as a kind of filter bank, but the nerve pulses going to the brain tend to synchronize with the waveform of the sound up to about 4 kHz to 5 kHz in humans. This leads to far better pitch perception than at higher frequencies, which is why the fundamental frequencies of musical instruments are usually no higher than about 4.5 kHz. The article I linked to in post #7 also leads to the conclusion that humans use more information than just the magnitude of the spectrum.