590 



Appendix A 



TABLE I 

 Terms Used in Physical Characteristics of Sound 



Quantity 



Symbol 



Quantity 



Symbol 



Subjective Equivalents 



f Pitch or tone ~ Frequency 



jLoudness ~ Sound pressure level 



f Quality or timbre ~ Harmonic content 



■f Discussed in Chapter 1, Section 2. 



where £ is the displacement, t is the time, v is the frequency, and A 1 

 and A 2 are constants (either of which may be zero). This is referred to 

 as a simple harmonic motion, or as a pure tone. The resolution of a 

 complex motion into simple harmonic terms was illustrated in Figure 1 

 of Chapter 1 . This type of analysis, known as Fourier analysis, can be 

 applied to any complex time dependent phenomena. Because any 

 speech pattern or any other sound can be represented as a sum (or 

 integral) of simple harmonic terms, most of the following discussion will 

 be restricted to single frequencies. 



In discussing sound waves, it is easiest to start from the particle dis- 

 placement £ which represents the distance a particle is displaced from 

 equilibrium. Because £ is a function of time, its first and second 

 derivatives, the particle velocity v, and the local acceleration a, will, in 

 general, be different from zero. For many acoustic analyses, v is slightly 

 easier to manipulate than is £. 



Particularly, if £ is simple harmonic, it is convenient to use the so- 

 called "complex notation." In this procedure, £ is represented by a 

 complex number which is easier to manipulate than the real part. Only 



