Sound and Hearing - Posted on 2013-02-28 by Eric Sullivan

Hey everyone!

This week was all about the subject of sound and hearing! I learned how all sounds are created by causing a certain medium to vibrate. The sound travels by making adjacent particles vibrate together until it eventually makes it to our ears. The graphical representation of the signals amplitude at a given time is what is known as a waveform. If two identical sound waves are played and one is slightly further along in its cycle than the other, a delay is created. This is called being "out of phase". You can have two identical waveforms that are 180 degrees of out phase from eachother and they will cancel eachother out completley!

Humans hear a frequency range from about 20 Hz to around 20,000 Hz. The frequency of a sound determines its pitch. Ultrasonic sounds are sounds higher than we can hear and infrasonic sounds are those lower than we can hear. Just how sounds can have different pitches, they also have different intensities. Sound volumes are measured using the decibel (db). To put it into perspective, an audible whisper is around 30 db. An average conversation is around 60 db and the threshold of pain is around 130db such as a jack hammer or a pig squeal! When the pig squeals, we can tell its location through binaural localization. We use this three different ways. Inter-aural intensity is telling a location based on the fact that the sound arriving to the closest ear has a higher intensity than when it arrives at the second eart. Inter-aural arrive time difference calculates which sound arrived first with regards to low frequencies. The final one being the pinnae of our ears reflecting the sound and creating time delays that further clue us in on the sources location.

I hope you enjoyed this brief crash course in sounds and hearing!  Next up is Studio design and monitors!