Room Acoustic Scale Model Measurements using a "Spark Train"

The spark gap, used as a sound source in scale model investigations, has advantages and disadvantages. One of the advantages is its limited size, which is particularly important for investigations at small scales. Also, the spark gap is omnidirectional and can be constructed such that the shape has a negligible influence on the sound field to be measured, for any scale factor. A disadvantage of an excessive discharge is the appearance of a shockwave. This leads to non-linear effects that make it impossible to acquire reliable impulse responses at small distances from the spark gap. A second disadvantage is the spread in successive separate impulse levels as a result of the micro-climate near the spark gap. Experiments were performed with a low energy spark gap (maximum electrode separation of 8 mm). In these experiments the energy was spread over a longer time interval through the use of spark trains. This allows for high INR values and reliable measurements of sound pressure levels. The period stability (jitter) of the spark train and spread in strength of the individual discharges were studied.