Evaluation and improvement of a model to predict the measurement uncertainty due to the directivity of room acoustical sound sources

Abstract

With the aim to reduce the necessary efforts to empirically determine the uncertainty in room acoustical measurements, in previous work, a model was developed that can predict the uncertainty a directivity of a sound source introduces to a measurement. As part of the validation extensive series of scale measurements have been conducted. In this contribution, the predicted uncertainty based on simulations and the empiric data is compared to each other. The results were used to improve the model. Concluding it will be discussed whether the model is suitable for a reasonable measurement uncertainty discussion.

Measurements in Room Acoustics How Good Are We at It

“…Today the measurement procedure can be considered generally accepted and research discusses different influences and their effect on the uncertainty. Among other influences investigations target the directivity of sound sources (Knüttel, Witew, & Vorländer, 2013;Leishman, Rollins, & Smith, 2006;San Martin, Witew, Arana, & Vorländer, 2007;Witew, Knüttel, & Vorländer, 2012;Witew, Müller-Giebeler, & Vorländer, 2014), the directivity of receivers (Witew & Behler, 2003;Witew, Lindau, et al, 2013), the position of the receiver (de Vries et al, 2001;Witew, Behler, & Vorländer, 2004;Witew & Vorländer, 2011) but also the algorithm to analyse impulse responses (Guski & Vorländer, 2015;Katz, 2004;Witew & Behler, 2005). This multitude of individual studies makes it difficult to reach an aggregate perspective and thus to distinguish significant from more moderate influences.…”

Measurements in room acoustics

“…Today the measurement procedure can be considered generally accepted and research discusses different influences and their effect on the uncertainty. Among other influences investigations target the directivity of sound sources (Knüttel, Witew, & Vorländer, 2013;Leishman, Rollins, & Smith, 2006;San Martin, Witew, Arana, & Vorländer, 2007;Witew, Knuettel, & Vorländer, 2012;Witew, Müller-Giebeler, & Vorländer, 2014), the directivity of receivers (Witew & Behler, 2003;Witew, Lindau, et al, 2013), the position of the receiver (de Vries et al, 2001;Witew, Behler, & Vorländer, 2004; but also the algorithm to analyze impulse responses (Guski & Vorländer, 2015;Katz, 2004;Witew & Behler, 2005).…”

“…The implied model suggests a constant uncertainty contribution over the running time of the impulse response. Using a very large data collection, Witew et al (2014) have shown that the uncertainty of the impulse response due to the source's directivity changes over the running time of the impulse response. The very early parts of the impulse response show a significantly higher uncertainty compared to the later parts of the (diffuse) exponential decay.…”

“…Shape and volume Based on the above considerations, the room acts as a secondary influence quantity on the uncertainty of room acoustical measurements. This can be illustrated using the studies by Witew et al (2012) and Witew et al (2014) as examples. In extensive measurement series, the influence of the loudspeaker directivity on measured room impulse responses was investigated.…”