Airborne sound insulation in terms of a loudness model

Abstract

A B S T R A C TOne of the main goals of building acoustics is the prediction of airborne sound insulation between rooms to determine the quality of sound protection. In many practical cases, however, the objective measures of the airborne sound insulation using procedures in standards are not in agreement with the subjective assessment. This paper, therefore, after reviewing the conventional model to calculate airborne sound insulation, introduces a calculation scheme based on loudness level linked with specific fluctuation strength, yielding a weighted normalised loudness level difference, L nor,w . By analysing the difference between standard airborne sound insulation values and the introduced weighted normalised loudness level difference, it is revealed that the sound pressure level that is transmitted through a partition decreases with increasing frequency, and this is independent of the type of signal and of the airborne sound insulation values (R' w -values), whereas if the transmitted signal is converted into a loudness level, it tends to rise with increasing frequency. Moreover, it is found that, whereas a simple level difference does not exhibit the effect of a given signal to the frequency-dependent airborne sound insulation curve, using L nor,w , a significant change can be observed, in terms of both computed and measured results. Furthermore, the frequency-dependent results allow more details to be investigated for a certain sound insulation. A comparison between the measured and predicted airborne sound insulation with no obvious malfunction suggests that at some frequency ranges, a hypothetical subjective related failure might occur. Overall, the proposed L nor,w could reveal detailed insights into the in situ measured airborne sound insulation compared with standard airborne sound insulation values. The frequency-dependent values discussed in this paper form a basis for developing a single-number index.

Advanced Rating Method of Airborne Sound Insulation

“…The study supports results presented earlier [8] that an index of sound insulation expressed as a single number rating (such as the weighted sound reduction index) cannot provide a reliable measure of the perceived efficacy of the insulation.…”

“…This is only true if sound pressure level differences or even loudness level differences are concerned [8].…”

“…The advanced rating method as introduced by Neubauer and Kang is given as the frequency-dependent weighted normalized loudness level difference, as shown in Equation (1) and is described in detail in [8].…”

“…Neubauer and Kang introduced a concept describing a frequency-dependent weighted normalized loudness level difference [7][8][9]. This concept is intended to be a connection between the objective measure of airborne sound insulation and the psychoacoustic measures of the loudness level and fluctuation strength.…”

Factors influencing low-frequency noise reduction in typical Chinese dwelling layouts

“…11,12 Low-frequency noise reduction and control are difficult, because outdoor to indoor noise reduction by walls and other structures, as well as hearing protectors, generally decreases with frequency. [13][14][15][16] Also, low-frequency noise suffers less attenuation due to distance and transmission loss by the environment. 17 These factors make it more difficult to reduce low-frequency noise, as its natural attenuation is only 20 dB over a distance of 500 m. 18 Access to a quiet side of a dwelling, on the other hand, might have the potential to efficiently reduce residents' subjective experiences of low-frequency noise levels.…”