time delay spectrometry (measurement) (TDS)

Time Delay Spectrometry (TDS) is a measurement method used in room acoustics and architectural acoustics in cases of severe noise disturbance.

The basis of this measurement method is a linear sinusoidal sweep in which the excitation signal is sinusoidal and the instantaneous frequency increases or decreases linearly with time. This relationship between instantaneous frequency and time allows delay times to be expressed as frequency differences. During the measurement, a tracking filter can be looped into the signal path whose center frequency changes at the same rate as the instantaneous frequency of the sinusoidal sweep. In this way, by adjusting the filter parameters, it is possible to emphasize or suppress certain time ranges in the frequency domain.

The TDS method can be used, for example, to mask room reflections when measuring loudspeakers.