Sound Of the Month Edition

Message right to your brain

Understanding sound impact on human mind

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Before reading further, please listen to the above sample.

It is a basic 880hz sine wave with applied irregular silence intervals (randomized square tremolo).

Project settings

Majority of the population would interpret the above signal as a Morse code. Some would try to decode it. I bet you got curious about the message and are hoping for me to explain it. I must disappoint you – those are just a random silence/sound intervals. Falasol can go like this forever…

Let’s take a second look at what just happened: Your mind categorized a sound according to some learned pattern (Morse code). That triggered thoughts (what might be the message?) and emotions (feeling of curiosity). And quite likely I was able to predict that :)

Starting with this example I will attempt to trace the full path from the initial sound source to resulting human thoughts (and any other impacts). Wherever possible I include examples and links for further reading.

Sonic route overview

from air wave to human action

1. Sound source

   The physical object producing sonic waves. Other impacts come from: position – determines the direction from which the sound will be heard movement – causes the change direction and can impact the pitch via Doppler effect

2. Physical carrier

   Usually air or any other gas, but also might be liquid or solid object. There can be influences from: carrier movement (wind) density changes (helium voice effect) wave reflections (echo) decay of certain frequencies (music coming from behind the wall usually have higher frequencies filtered out) wave interference (tremolo effect on 2 slightly detuned strings) background noise

3. Ear

   The human hearing organ. amplification of some frequencies (~1kHz – 3kHz) (middle ear) limited frequency range detection (~20Hz – 20kHz) conversion to neural signal in frequency domain – individual cells get excited by sounds at specific frequencies, or multiples of that frequency. Every human comes with an FFT circuit built in! (inner ear / auditory cortex) other parts of human body can detect loud & low frequencies as well (turn up the subwoofer and put your hand in front of it :)

4. Reflex responses

   .

   shock reaction on unexpected sudden noise (or attention draw on less rapid changes) volume sensitivity adaptation (clock ticking ignorable during daytime can get extremely annoying at night when everything else is quiet) brainwave entertainment – I realize most people put that term somewhere between Aliens, Atlantis Rings and Global Warming, but this phenomenon is observed experimentally, measurable (EEG) and reproducible. We still might be missing full understanding of all the mechanisms involved in it though non audible impacts – this domain is still a fringe science. I was not able to confirm the below influences (due to lack of equipment and volunteers). Some might be as well just urban legends – but it’s interesting enough to mention: ultrasounds (>20kHz) – hypersonic effect (source article) – pleasure, good vibrations infrasounds (<20Hz) – anxiety, sorrow, fear: negative vibes (often used in thrillers). Other funky effects include resonance frequencies of various human body parts: eyeballs – ghost vision (other article, more toys) bowels – brown note (myth-busters episode – not sure though how the earplugs were supposed to protect the witnesses :)

5. Subconscious / semi-conscious processing

   auditory scene analysis filtering out noise & background voices (listening to the conversation at the cocktail party) matching the information with other senses (lip-synced animation – looks like animated characters are really speaking) space & environmental mapping – retrieving source location & environment information from sound distortions (echoes, timbre changes, direction) – feel it on your own: virtual barbershop ; other nice concept: COD MW 2 teaser quick sound classification: speech, cry, animal noise, accident crash, instrumental tone etc. emotional triggers: fear, curiosity, happiness (on familiar voice), alert, disturbance (by leaking tap), empathy (someone else is laughing or crying) phonological loop – speech recognition, harmonic succession feeling (and possibly rhythm)

6. Interpretation

   .

   speech & emotional recognition (What is the message and my first reaction to it?) “This guy says it’s all gonna be ok, but his voice is shaky. I don’t trust him.” “This song makes me sad, feeling like I lost something precious” “Wow, that was bullshit!” recalling similar sounds & patterns from memories (Did it happen before?) “I’ve heard this song before! It was my on the night when I got kicked out from the club.” “Her rough accent reminds me of my math teacher.” “Last time she said exactly the same and it was untrue.” conclusions: (What does it all mean to me? - based on all of the above: experience, subconscious decisions, info retrieved from the sound, emotions, memory, current attitude…) “There is emergency signal close to next block. Something might have happened to my neighbor!” “Nice look and smooth talking, but in the end it’s all about cutting my salary.” “My car sounds a bit different, there must be something wrong with gas.”

7. Afterthoughts and further actions

   all the hard thinking and acting that take place once the initial stimulus is fully processed “Let’s help that poor animal it’s suffering!” “Party on! Where’s da beer?!” “Something’s going on there, I should get my cell-camera ready.”

I hope the above analysis can help controlling human mind better. I’m also going to use it for further project development plans. Feel free to comment if you think I missed something.

Come get SoME!

Update (27 Nov 2011): Added non audible impacts in point 4. Thank you girl in green for pointing that out! :)