Glossary beginning with R
- recording level
"The strength of a recorded sound; teh setting of the recording equipment control that determines this strength." 
- resonant frequency
"The frequency of an oscillating system at which the maximum amplitude of oscillation occurs in response to adriving force." 
"The frequency at which resonance occurs in a system. N.B., this and natural frequency are not the same thing, though often used as if synonymous by bio-acousticians... this is the frequency an applied periodic force of minimal value has to have in order to keep the system vibrating. It is clealry higher than the natural frequency." 
- . Arthropod Bioacoustics: Neurobiology and Behaviour. Ithaca, New York: Comstock; 1989.
- . Glossarial Index. In: Acoustic Behavior of Animals. Acoustic Behavior of Animals. Elsevier; 1963.
- resonant song
"A song with almost pure dominant frequency. If thsi frequency is sufficnetly low, as is common in crickets, the song has a clear musical pitch." 
See Rivalry song
- rivalry song
"The special song produced by two or more males reacting to one another." 
See Calling song