Influence of a forest edge on acoustical propagation: Experimental results

Abstract

Acoustic propagation through a forest edge can produce complicated pressure time histories because of scattering from the trees and changes in the microclimate and ground parameters of the two regions. To better understand these effects, a field experiment was conducted to measure low-frequency acoustic pulses propagating in an open field, a forest, and passing through a forest edge in both directions. Waveforms measured in the open field were simple impulses with very low scattering, whereas waveforms at the edge and within the forest had stronger reverberations after the direct arrival. The direct wave pulse shapes increased in duration in accordance with the path length in the forest, which had an effective flow resistivity 12 to 13 that of the grassy open field. The measurements exhibit different rates of attenuation in the two regions, with relatively lower attenuation in the open field than higher rates in the forest. Decay of SEL transmitted into the forest was 4 dB more per tenfold distance than for outbound transmission. Stronger attenuation in the 1-2 kHz range occurs when propagating into the forest. While the measured meteorological profiles revealed three distinct microclimates, meteorological effects are not sufficient to explain the apparent non-reciprocal propagation.

Are quartzite scree slopes used by birds to promote sound transmission in the Mediterranean forest?

“…Therefore, when the sound waves reach such surfaces, a high percentage of the sound energy is reflected. In contrast, some elements present in the forest, such as bare earth and forest mass, contribute to sound attenuation (Bucur, 2006;Swearingen et al, 2013). The lower attenuation of bird sound on reflective surfaces has been shown in previous studies (Yip et al, 2017).…”

Atmospheric Sound Propagation over Rough Sea: Numerical Evaluation of Equivalent Acoustic Impedance of Varying Sea States

“…For many decades, atmospheric sound propagation studies have been conducted predominantly on land [1][2][3][4], with only a few studies conducted over sea and small bodies of water [5]. In recent years, research on sound propagation in coastal areas has garnered increased interest, driven by the growth of off-shore wind farms [6][7][8], oil and gas platforms, offshore airport construction [9], and other activities.…”

Airflow resistance of acoustical fibrous materials: Measurements, calculations and applications

“…The sound absorption properties of fibrous materials can be predicted from airflow resistance through modeling approaches, such as the famous Delany-Bazley empirical model and its modifications [17–20]. Airflow resistance is widely used to evaluate the potential acoustical applications of various porous materials, such as sugarcane waste [21], recycling coal bottom ash [22], natural jute fibers [23], indoor plants [24], forest edge [25], periodic groove structure [26], wood-wool cement board [27] and bimodal structured polylactide foams [28]. In this paper, we have mainly reviewed the measurements, calculations and applications of airflow resistance.…”