Sound Localisation

Human ears are a unique pair of organs to look into. Without opening our eyes, we are able to detect sound from various positions around us. Being able to localize sound enables us to detect a vehicle approaching without the need for us to turn our head. Imagine a sound source is on the right hand side of you, sound will reach your right ear before the left ear. Also, the sound from the right ear has a higher level than the left ear because the head shadows the left ear.

There are two main ways for our ears to localize sound.

(1)Interaural Time Differences (ITD)

(2)Interaural Level Differences (ILD)

Low frequency sound which is approximately below 1500Hz gives rise to ITD.  In contrast, high frequency sound which is approximately above 1700Hz gives rise to ILD. This is because our head acts like a low pass filter and much of the high frequency sound gets reflected off thus reducing the sound levels being reached to the other ear. These mentioned frequencies vary as the size of the head differs from one person to another. For frequencies in between 1500Hz and 1700Hz, both roles ITD and ILD play a part in being able to localize sound.

Knowing the fundamental of sound localization, it is possible to use this critical information in audio production. In stereo recording, both panning and level are used to simulate a real live band performing in front of us.

Youtube is a good website to find some audio and acoustics related stuffs. Some of the users provide an easy way to understand the materials so that you would have some idea about it. The video below explains and demonstrate how sound localization is being tested.

Do you agree with my blogpost?  Feel free to comment it. 🙂

 

References

(1)  Sound Localization

http://www.open.edu/openlearn/science-maths-technology/science/biology/hearing/content-section-12.1

(2) Perception

http://www.lifesci.sussex.ac.uk/home/Chris_Darwin/Perception/Lecture_Notes/Hearing5/hearing5.html