Measuring with noise? We can do better!

Abstract

It has long been established that correlation-based measurement techniques, using, e.g., maximum length sequences and swept sines, outperform classical methods based on random Gaussian noise. Among the advantages of these modern techniques are better rejection of background noise and reduced measurement duration to achieve similar or better precision. These advantages are especially interesting in room and building acoustics, where many measurement positions typically have to be covered and background noise is often an issue, especially when measuring sound transmission loss or velocity level differences. Unfortunately, there is currently no provision in the ASTM standards on room and building acoustics that would allow the use of these modern measurement methods. To demonstrate the advantages of these methods, this contribution will present an example of measurements of the apparent sound transmission loss, i.e., measurements of sound pressure level differences and reverberation times. In addition to the standardized measurements according to ASTM E336, all measurements were repeated with maximum length sequences and swept sines. The results will be compared and the advantages of the modern techniques will be highlighted.

Measurements in room acoustics

“…Dynamic measurements in the presence of noise Measurements using 2-Ch-FFT correlation techniques are widespread, are a standardized approach (ISO 18233, 2006) and are considered extremely reliable and robust against disturbances (Müller & Massarani, 2001;Müller-Trapet & Höller, 2018). Discussing the associated uncertainty is challenging as the classical GUM method requires establishing an algebraic relation between the system's stationary input and output quantities.…”