ELEMENTARY EXPERIMENTAL PHYSIOLOGY 11 



6. What Qualities of Sounds are Perceived? 



(i) Loudness. What is this due to? 



(ii) Pitch. What is this due to ? 



Is the perception of pitch limited ? Using tuning forks for the 

 lower limit and the steel cylinders supplied for the upper limit, 

 determine the range of perception of musical sounds. 



(iii) Quality, (a) Sound the tuning fork doh strongly, and note 

 the character of the resulting sensation. 



(6) Repeat the experiment, and immediately after sounding the 

 fundamental tone, sound the three partials me, soh and doh above, 

 and note the character of the resulting sensation. 



Formulate your conclusions as to the influence of overtones upon 

 the quality of musical tones. 



7. Do Sound Vibrations influence the Internal Ear only through the 

 External Ear ? 



METHOD. Sound a tuning fork lightly, and hold it to the ear 

 until the sound has quite died away. Now place the end of the 

 fork against the closed teeth or the mastoid process. Describe the 

 resulting sensation. What conclusion do you draw ? 



Grip your watch between your teeth and close one ear and then 

 the other. Note the sensations. Repeat the experiment with the 

 watch between, but not touching, the teeth. Compare and explain 

 the results. 



8. Is the Power of Localising the Source of Sound well developed ? 

 Test the power of localisation by making a faint clicking noise 



as by closing sharply a pair of forceps in the neighbourhood of 

 the head of the subject whose eyes are closed. The latter must 

 make a definite statement as to the direction from which the sound 

 comes. 



(Read Physiology of Hearing in Text Book.) 



VOICE 



(Revise the anatomy of the larynx.) 



Laryngoscope. Fix the mirror of the laryngoscope on the 

 forehead. 



A. Examine the model of the larynx by projecting a beam of 

 light into the mouth cavity and inserting the small mirror on the 

 handle into the back of the throat so that the beam is reflected 

 downwards into the trachea. Identify the structures represented. 



B. Place a fellow student in one of the stalls in the dark room 

 with a light beside his head, and let him open his mouth widely. 

 Gently warm the small mirror on the handle. Hold down the 

 tongue in a fold of handkerchief. Reflect light into the mouth by 

 means of the mirror on the forehead, and insert the small mirror 

 through the pillars of the fauces and try to see the upper opening 

 of the larnyx reflected in it. 



