HANDBOOK OF ACOUSTICS - online book

A complete view of Acoustical Science & its bearings on music, for musicians & music students.

Home | Just The Tune | Order | Contact




RESONANCE.
67
chapter. Starting with the resonator at this length, by gradually increasing or diminishing its length, while that note is being sounded on some instrument, a point of maximum resonance will soon be obtained. In this way, the length of the resonator for all the notes within its range can be ascertained. The names of these notes may be conveniently written on a slip of wood, or engraved on a strip of metal, each one at a distance from the end equal to the length of the resonator, when tuned to the corresponding note-Then, in order to adjust the resonator to any note, it is only necessary to place the slip inside it, and gradually lengthen or shorten till the open end is coincident with the name of that note, as engraved on the slip. It is of great advantage to have two such resonators, both similarly tuned, and simultaneously apply one to each ear. If only one be used, the other ear should be closed.
For sounds high in pitch, glass tubes cut to the proper lengths, are very convenient. They may be made to taper at one end for inser­tion in the ear, or in the case of very high notes, left just as they are, and used as open tubes, being held at a small distance from the aural passage. It may be remarked here, that the tube of the ear is itself a resonator. The pitch of the note to which it is tuned, will of course vary in different person s, and may in fact be different for the two ears of the same person; it generally lies between Q-3 = 3,072 and E3 = 2,560.
Summary.
Resonance or Co-vibration is the name given to the phenomenon of one vibrating body imparting its vibratory movement to another body, previously at rest.
To obtain the maximum resonance two conditions are essential:
(1)  The two bodies must be in exact unison; that is to say, they must be capable of executing precisely the same number of vibrations in the same time.
(2)  A certain period of time must be allowed for the exciting body to impress its vibrations on the other.
The phenomenon of resonance may be illustrated by means of tuning-forks, strings. &c, but partially confined masses of air are the most susceptible.
A Resonance Rox is usually constructed of wood; it may be open at one or both ends, and must be of such dimensions that the en­closed mass of air will vibrate in unison with the tuning-fork to be applied to it.