446 



Acoustics. 



NIL 53481 



53 500. 1 : 6. 



53 485. 1 : 4. 



53486. 1:7. 



53492. 1:4. 



Tonometric Apparatus and Resonators. 



Tone Variators after Prof. Stern, Figures 53,485, 53,486, cf. also Fig. 53,506, the tone 

 being varied steadily and uniformly (Ztschr. f. Psychologic und Physiologic der Sinnes- 



s. (1. 



The apparatus is suitable for demonstration purposes and for tuning, for psychological investi- 

 gations and practical investigations by otologists. 



The tone variators are brass flasks with zinc cap and blowing tube. The flasks have an adjustable 

 bottom which is raised by a spiral shaped disc in such manner that equal angles of rotation of the 

 disc correspond to approximately the same variations in periodicity. The periodicities can be ivjnl 

 off direct on the dial. In addition to the values of the periodicities, the musical tones in International 

 Pitch are given on the dial. 



Calibration is made by means of the blowers listed under Nos. 53,229 and 53.230. these blowers 

 supplying a very uniform pressure. It is advisable to use such a blower for the tone variators so that a 

 uniform pressure may be introduced into the apparatus. For observing the pressure when blowing every 

 tone variator is provided with a pressure gauge on the scale of which is marked the pressure at which 

 the tone variator is adjusted. 



The formation of a progression of tones from the single flasks can be introduced at the wish of the 

 customer. It is advisable to select the flasks so that the successive compasses of tone partially overlap, 

 since it is necessary in a number of experiments to sound two similar or closely adjoining tones simul- 

 taneously. 



An accurate description is appended to each apparatus. 



Prof. Stern, simple pattern, Figure, suitable for demonstration 



Tone Variators si ft or 

 purposes only. 



Compass 



In this apparatus the bottom of the pipe is not displaced by :i spiral, but by rack and pinion. An 

 excentrically operated pointer indicates the number of vibrations on the scale. 



53,495. Tonometer No. 1 of 33 tones: Fundamental Tone C = 128 compound vibrations to 

 c t = 256 (ut 2 = 256 v. s. to ut s = 512 v. s.), each BUCCeding tone about four compound 



vibrations higher than the preceding !'. n. 



The Tonometers and Overtone Apparatus fit all our Blowing Tables. 



Please observe also die Hezold's Continuous Tone-Progression Apparatus, 

 No. 53.473. also the single tuning forks and pipe* for same. 



(I. 1109, 



1112, 5819, 1112. 



