Question (submitted 10/14/04):

Using tuning forks, the smaller the tuning fork the softer the sound, the lower the pitch. If you compare the small tuning fork to a larger one, making a higher pitch...do the sound waves of the larger tuning fork travel through a medium faster than the smaller one? I was thinking that sound would travel through a specific medium at the same speed, no matter what the pitch. Can you help me out?

Response:

Your question deals with the nature of the sounds waves produced by the tuning fork. To begin, let's discuss the difference between pitch and frequency. The frequency of a vibrating object is the number of times that object vibrates per second (measured in Hertz, Hz). The vibrating object produces a sound wave with a similar frequency. Pitch is sometimes defined as the perception of the frequency of sounds waves. When discussing the properties of sound waves, physicists tend to use frequency instead of pitch. The pitch of a sound is usually spoken of in terms of its position on a musical scale. The note, A, has a range of fequencies between 436 Hz and 448 Hz, depending on the orchestra (for more information on this, see Conceptual Physics by Paul Hewitt, that is the source of my frequencies for the note A). So as you can see, the frequency of the sound is more fundamental than the pitch since the frequency is a more objective measurement of the property of the wave.

To answer your question, the speed of the sound wave emitted by the tuning fork does not depend on the frequency of the sound wave. The speed of the sound wave depends on the medium (material) that the wave is passing through. For example, the speed of sound in air is about 343 m/s while in iron the speed of sound is 5130 m/s. So you are correct, sound waves do travel through a specific medium regardless of their frequency.

Dr. Eugene Mosca of the United States Naval Academy pointed out that I missed something in regards to the question. Tuning forks with longer lengths produce sounds that have lower pitches (and frequencies). Dr. Mosca also included a website that illustrates this.