REPEATABILITY OF THE BALLOON POP AS A SOUND SOURCE IN A ROOM

A range of sound sources are used in the industry and in research to generate impulsive sounds to excite acoustically a space and obtain its response to that excitation. Room acoustic parameters, such as Reverberation Time (RT) can be derived from that impulse response (IR). The (party) air-filled balloon pop (or burst) is a type of sound source widely employed [1-6] for producing impulsive sound excitations (see figure 1). The popularity of this source is owed to its many convenient and practical merits [1]. These include quick deployment, low cost, simplicity of operation, low weight, high portability and relatively high sound pressure levels (SPL).

There is limited information in the literature reporting the suitability and reliability of the air-filled balloon pop as a sound source to obtain room acoustics parameters. In a comparative study Horvart et al [6] contrasted the peak SPL and spectra produced by firecrackers and balloons of three sizes. However, they failed to provide information on the number of samples used or repeatability of results. Cheenne et al [7] observed that the balloon diameter on its own is not a good predictor of radiated energy or spectrum. They defined a diameter factor (DF) in an attempt to overcome the variability of balloons due to resulting sizes and shapes when inflated. However, this study did not provide details on the balloons utilised and repeatability of results. A more complete study undertaken by Pätynen et al [8], studied the directivity and spectral content of various sizes of air-filled balloons bursts measured in an anechoic chamber. The study provided details of average peak SPL values and repeatability information for different balloon sizes. However the number of samples for some sizes was insufficient to report reliable repeatability. The study did not investigate the effect of repeatability on any room acoustic parameter.