Pitch response to human hearing

You need computer speakers with a dynamic range including 100 Hz.

  1. Periodicity Pitch
  2. fundamental tracking
  3. Aural Harmonics
  4. Combination Tones

 

 

  1. Periodicity Pitch:

If two harmonics of the same harmonic series are sounded together our ear will pick up the fundamental frequency.

 

      The sound sample contains the following sequence:

                  500 Hz/ 750 Hz together, followed by the 250 Hz fundamental

                  900 Hz/ 1200 Hz together, followed by the 300 Hz fundamental

                  700 Hz/ 1050 Hz together, followed by the 350 Hz fundamental

 

Pick up and hum the fundamental during the combination of the harmonics.

Compare to the fundamental.

 

  1. Fundamental Tracking:

You can follow the fundamental through changes in the harmonics.

 

The sound sample contains a sequence of

                  300 Hz/ 400 Hz

                  400 Hz/ 500 Hz

                  500 Hz, 600Hz

 

All of them have the same fundamental frequency of 100 Hz.

 

  1. Aural harmonics:

      Due to the non-linear response of the human auditory system, additional frequencies are heard if a simple sound wave arrives at the ear drum. These additional frequencies become audible if the amplitude of the sound wave is very large. Their frequencies are harmonics of the primary tone. We can make them audible by producing a beat frequency with the aural harmonics.

 

Sound sample A contains a 400 Hz simple tone. Vary the volume and observe.

 

Sound sample B contains the following sequence:

                  400 Hz

                  400 Hz joined by 802 Hz

                  400 Hz joined by 1202 Hz

 

Try the following experiment: Increase and decrease the volume of the simple tone. You will hear high metallic overtones at loud volume. This is the nonlinear response in form of aural frequencies.

The aural harmonics of a 400 Hz simple tone are 800 Hz, 1200 Hz, 1600 Hz, etc. These sounds originate in the cochlea, and are not part of the physical sound wave in air. If an 802 Hz sound is added, it will beat with the 800 Hz aural harmonic at 2 Hz.

This effect vanishes if you decrease the volume down to the region of linear response of the ear.

 

  1. Combination tones:

If two simple sound waves are received by the ear, they will create aural harmonics that are sums and differences of the two primary frequencies as in

 

The sound sample contains the sequence

                  300 Hz/ 400 Hz

                  300 Hz/ 400 Hz combined with 702 Hz

                  300 Hz/ 400 Hz combined with 1102 Hz

 

Examples of combination tones of 300 and 400 Hz are 700 Hz (m=n=1) and 1100 Hz (n=1, m=2). Listen for the beats with 702 Hz and 1102 Hz. Also, vary the loudness and observe the beats vanishing when the loudness is beck in the region of linear response of the ear.