In impulse response measurement, the time between outputting the signal to receiving the signal by the microphone can be measured, so the amount of delay in the output system can be measured by subtracting the delay due to the distance between the speaker and microphone from the delay time.

For example, if a microphone is placed 1m from your test target and the response is measured, and 1m is converted from the speed of sound to time and subtracted, then the delay time can be obtained and the frequency characteristics can be derived by applying the FFT analysis to the impulse response.