Swept Sine

A swept sine (also called exponential sine sweep or ESS) is a test signal that continuously sweeps through frequencies from low to high at an exponentially increasing rate. When used for impulse response measurement, the room response is deconvolved from the excitation signal to yield a clean impulse response. The swept sine technique, formalized by Farina (2000), offers significant advantages over MLS: superior rejection of harmonic distortion (which separates into distinct pre-responses), excellent signal-to-noise ratio (typically 60–80 dB), and immunity to time-variance artifacts. ISO 18233:2006 endorses swept sine as a preferred measurement technique. Typical sweep durations are 5–20 seconds, with longer sweeps providing better SNR. The method requires a loudspeaker capable of reproducing the full frequency range without severe distortion. Swept sine is now the de facto standard for room acoustic measurements worldwide.