Using synthesised musical stimuli to measure room impulse responses in occupied spaces

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Since Sabine instigated objective parameters a century ago, the advance of room acoustics has been centred around measurement findings. Room impulse responses are of particular importance: nowadays, measurements typically start from impulse responses, individual acoustic parameters are then derived. With existing methods, noisy signals intolerable to audience are employed as stimuli to obtain the impulse responses. Consequently, occupied measurements are rarely carried out. Unoccupied measurements are unreliable and problematic, because they do not accurately represent the acoustic profile under in-use conditions. This paper presents a method that utilises “presto-chirps”, short chirps centred on musical notes in an equal temperament scale, to synthesise musical notes. The harmonics might be added by the Volterra kernel convolution, if richer tones are preferred. These musical notes are used to compose synthesised music as test stimuli. Room impulse responses are deconvolved from received signals in musical note specified sub-bands. Following energy normalisation and superposition broadband impulse responses are obtained. The use of musical stimuli facilitates occupied measurements. The purpose-defined presto-chirp enables the measurement to be completed in a relatively short duration, mitigating time variance problems.