ON THE VIABILITY OF THE ENERGY-TIME CURVE (ETC) IN ELECTRO-ACOUSTICS MEASUREMENT AND ANALYSIS

The Energy-Time Curve (ETC) is often recommended as a useful tool for examining acoustic reflections in a room, particularly when evaluating an electro-acoustic system. It was first proposed by Heyser1 in 1971 as an addition to his time-delay spectrometry (TDS) analysis methods for the determination of loudspeaker arrival times. The ETC is the envelope of an impulse response and is used with the intent of providing a view of the time domain free of the interference effects of a linear or logarithmic impulse response plot2 . It is the magnitude of the analytic signal, which is a complex-valued extension of an impulse response, consisting of the impulse response as the real part and its Hilbert transform as the imaginary part. Despite being a fixture in acoustic analysis software, there is not wide agreement on its practicality in terms of providing an enhanced view of time data, nor is there a thorough understanding of how it is derived. Through an extensive literature review and some preliminary analysis of real measurement data, this study investigates if and when the ETC is an appropriate tool to help aide decisions – both objective and subjective – in room acoustic and electroacoustic design and optimisation.