Sine waves are periodic, oscillating waveforms represented as sine curves and are elementary components of sound. The VTG 400D and VTG 400DVI generate sine waves with programmable amplitude between -72 dBu and +6 dBu, -74 dBV and +4 dBV, and frequency specified between 20 Hz and 20 kHz in 1/12 octave steps. Sine wave signals are used in testing and measuring the frequency response and distortion of audio products, as well as crosstalk between the left and right channels.