He found that when the resonator was placed in certain positions with regard to the oscillator, small sparks were seen between the micrometer balls, and when the oscillator was placed at one end of a room having a sheet of zinc fixed against the wall at the other end, symmetrical positions could be found in the room at which, when the resonator was there placed, either no sparks or else very bright sparks occurred at the poles.
This rate of loss for each amplitude was determined (i) when the fork was vibrating alone, and (2) when a resonator was placed with its mouth under the free ends of the fork.
The amplitude of the fork was observed when the sound just ceased to be audible at 27.4 metres away, and the rate of energy emission from the resonator was calculated to be 42 .
Physik, 1906, 21, p. 131) compared the indications of Wien's resonator manometer with those of V.
But the same resonator will be appreciably though less affected by waves of frequency differing slightly from its own.
He used a spherical Helmholtz resonator resounding to the tone to be measured.
If the harmonic corresponding to the resonator is present its tone swells out loudly.
There is not much difficulty in detecting the difference tone by a resonator if it is held, say, close to the reeds of a harmonium, and Helmholtz succeeded in detecting the summation tone by the aid of a resonator.
From a pinhole burner, fed through a cavity C, one side of which is closed by a membrane m; on the other side of the membrane is another cavity C', which is put into connexion with a source of sound, as, for instance, a Helmholtz resonator excited by a fork of the same frequency.