Measurement of sound power and absorption in reverberation chambers using energy density

Abstract

Reverberation chamber measurements typically rely upon spatially averaged squared pressure for the calculation of sound absorption, sound power, and other acoustic values. While a reverberation chamber can provide an approximately diffuse sound field, variations in sound pressure consistently produce uncertainty in measurement results. This paper explores the benefits of using total energy density or squared particle velocity magnitude (kinetic energy density) instead of squared pressure (potential energy density) for sound absorption and sound power measurements. The approaches are based on methods outlined in current ISO standards. The standards require a sufficient number of source-receiver locations to obtain suitable measurement results. The total and kinetic energy densities exhibit greater spatial uniformity at most frequencies than potential energy density, thus requiring fewer source-receiver positions to produce effective results. Because the total energy density is typically the most uniform of the three quantities at low frequencies, its use could also impact the usable low-frequency ranges of reverberation chambers. In order to employ total and kinetic energy densities for sound absorption measurements, relevant energy-based impulse responses were developed as part of the work for the assessment of sound field decays.

Modifikasi Permukaan Elemen Peredam Bising dengan Profil Berbentuk Prisma

“…Analisis serupa juga dilakukan oleh Nutter et al yang menggunakan pendekatan energy density. Sementara Hanyu serta Groby et al berturut-turut melakukan pendekatan teoretik dan eksperimental atas dampak pemakaian bingkai padat sebagai penopang sound diffuser terhadap kinerja redamannya [4][5][6][7] .…”

Evaluation of Decay Times from Noisy Room Responses with Pure-Tone Excitation

“…An accurate determination of decay times is primary for both absorption measurements in reverberation chambers (Barron, Coleman, 2001;Nutter et al, 2007) and the evaluation of acoustics of performance spaces (Bradley, 2005; Goła, SuderDębska, 2009; Adelman-Larsen et al, 2010; Beranek, 2011) as well as ordinary rooms (Díaz, Pedrero, 2005. Decay times are evaluated from a decay curve defined as the graphical representation of the decay of the sound pressure level in a room as a function of time after the cut-off of a continuous sound source (ISO 3382, 2012).…”

Study and development of an in situ acoustic absorption measurement method

“…With PU probes, the energy density can also be obtained. Energy density has the advantage of being more spatially uniform than potential energy density only, which is captured with microphones [147].…”

“…Usually, the potential energy is low at positions were the kinetic energy is high, and visa versa. Conventional microphone -based measurements are therefore position dependent, while the sum of the potential and kinetic energy density is more spatially uniform [147]. On the other hand, usage of the potential energy might be preferred in the near field of sound sources because it decays with 2 1 r in the same way as the active intensity does.…”

“…Simulations require much calculation power and small details existing in reality are usually disregarded. In [146,147] a method was applied to visualise sound intensity vector fields. It was shown that complicated sound intensity fields exist even around the simplest structures.…”