€8 Experiments on Audition. 



and though I do not anticipate that the observations contained 

 in this communication will lead to any important results, their 

 novelty may claim for them some attention from the readers of 

 your Journal- 



5 1- 



If the hand be placed so as to cover the ear, or if the en- 

 trance of the meatus auditorius be closed by the finger without 

 pressure, the perception of external sounds will be considerably 

 diminished, but the sounds of the voice produced internally will 

 be greatly augmented : the pronunciation of those vowels in 

 which the cavity of the mouth is the most closed, as e on, &c,, 

 produce the strongest effect ; on articulating smartly the sylla- 

 bles te and kew, the sound will be painfully loud. 



Placing the conducting stem of a sounding tuning-fork* on 

 any part of the head, when the ears are closed as above de- 

 scribed, a similar augmentation of sound will be observed. 

 When one ear remains open, the sound will always be referred 

 to the closed ear, but when both ears are closed, the sound will 

 appear louder in that ear the nearer to which it is produced. 

 If, therefore, the tuning-fork be applied above the temporal 

 bone near either ear, it will be apparently heard by that ear 

 to which it is adjacent ; but on removing the hand from this ear 

 (although the fork remains in the same situation) the sound 

 will appear to be referred immediately to the opposite ear. 



In the case of the vocal articulations, the augmentation is 

 accompanied by a reedy sound, occasioned by the strong agita- 

 tions of the tympanum. When the air in the meatus is com- 

 pressed against this membrane by pressing the hand close to the 

 ear, or when the eustachian tube is exhausted by the means 

 indicated by Dr. Wollaston, the reedy sound is no longer heard, 

 and the augmentation is considerably diminished. The ringing 



• The tuning-fork consists of a four-sided metallic rod, bent so as to 

 form two equal and parallel branches, having a stem connected with the 

 lower curved part of the rod, and contained within the plane of the two 

 branches. The branches are caused to vibrate by striking one end 

 against a hard body, whilst the stem is held in the hand. The sound 

 produced by this instrument when insulated is very weak, and can only 

 be distinctly heard when its branches are brought close to the ear ; but 

 instantly its stem is connected with any surface capable of vibrating, a 

 great augmentation of sound ensues from the communicated vibrations. 

 ThQ facility of its insulation and communication renders it a very conve- 

 nient instrument for a variety of acoustical experiments. 



