Examples of Tones & Noise

Example 1: A pure tone of 500 Hz--This a represents a periodic oscillation with energy concentrated at a single frequency toward the lower end of the speech range. These would be mostly vowels.(Actually, this is not as pure a tone as I would prefer. I notice a little distortion picked up during the recording process, and a little noise in the background also, but it is satisfactory for demonstration purposes. For research or actual use in testing hearing, we would have to do much better.)

Pure Tone 500 Hz Example 1

Example 2: A pure tone of 1000 Hz--This a represents a periodic oscillation with energy concentrated at a single frequency at the center of the speech range. This is the most sensitive frequency in human hearing. That is, it takes the least amount of engergy (intensity) for a pure tone to be heard at least 50% of the time (threshold). The actual value is .0002 dyne/cm2. For each higher and lower frequency, the intensity at threshold must be progressively increased.

Pure Tone 1000 Hz Example 2

Example 3: A pure tone of 4000 Hz--This a represents a periodic oscillation with energy concentrated at a single frequency toward the upper end of the speech range. These would be mostly consonents. Most audiometers test as high as 8000 Hz. A loss at this frequency would not effect speech but would be a medical "red flag."

Pure Tone 4000 Hz Example 3

Example 4: White Noise--This represents aperiodic (random) oscillation with energy invested equally at at all frequencies.

White Noise Example 4

Example 5: A Complex Tone--This a represents a periodic oscillation with energy concentrated at number of single frequencies (pure tones). The Pure Tones in this Complex Tone can be calculated and identified through Fourier Analysis. The lowest (called the Fundamental) determines the perceived pitch. the pattern of all the higher tones (called the overtones) determins the quality (recognizability) of the tone. For example:
The following tone (in example 5) can be recognized as being...

• a. A note played on a violin.
• b. A human voice
• c. A sewing machne
• d. The sound of a Jet
• e. The sound of a rancid pineapple landing in slow motion on the Kamehameha highway when dropped off the Pali in Hawaii.

Complex Tone Example 5

The answer was b.