Binaural Demos

These demonstrations are designed to reinforce your understanding of how different binaural cues give rise to the experience of spatial hearing.


1. Headphone test

Before you start …

You must ensure that you have stereo headphones

 (and, if your headphones are wired rather than wireless, they must be plugged into a stereo headphone jack)

                Mono:                                          Stereo:          

 

You can test your headphones with the following sounds.

(be careful that your volume setting is not too high!)

 

If your headphones are working correctly, you will hear:

1. This sound in your left ear only

2. This sound in your right ear only

3. This sound in both ears

 


2. Localization via interaural time differences (ITDs)

The following file contains

1. A 500-Hz tone in each ear with an alternating interaural phase difference (IPD) of +/- 45 degrees

2. A 2000-Hz tone in each ear with an alternating interaural phase difference (IPD) of +/- 45 degrees

Question 1: What are the ITDs corresponding to these IPDs for each frequency?

Try to figure it out for yourself and then click here for the answer.

 

Now listen to the file (courtesy of the Acoustical Society of America):

You should perceive a change in location for the 500-Hz tone but not for the 2000-Hz tone.

Question 2: Why is the perception different for the two tones?

Click here for the answer.

 


3. Localization via interaural level differences (ILDs)

The following file contains

1. A 250-Hz tone in each ear with an alternating interaural intensity difference (IID)

2. A 4000-Hz tone in each ear with an alternating interaural intensity difference (IID)

(note that intensity is synonymous with level in this context)

Now listen to the file (courtesy of the Acoustical Society of America):

You should perceive a change in location for both tones.

Question 3a: Why is there a perceived change in location for both tones? (i.e. why is the perception different for ILD than for ITD?)

Question 3b: Why is this demonstration very artificial?

Click here for the answers.

 


4. Binaural Beats

The following file contains a 250-Hz tone presented to the left ear and a 251-Hz tone presented to the right ear

Now listen to the file (courtesy of the Acoustical Society of America):

You should perceive a single tone circling around your head.

Question 4: Why would presenting two tones with slightly different frequencies create a perception of motion?

Click here for the answer.