An application of normal mode decomposition to measure the acoustical properties of low growing plants in a broad frequency range

A review of the application of green walls in the acoustic field

“…Efforts are also made to either develop a more comprehensive model to give a better prediction or optimize the absorption ability of green walls. To increase the upper frequency limit of the standard ISO 10532-2 method, Prisutova et al 11 used a larger impedance tube with a dimension of 14 300 mm × 300 mm × 4150 mm and applied the normal mode decomposition method 49 to measure the reflection and absorption coefficients of three low-growing living plants. The higher frequency limit was reported to be extended by a factor of 3.…”

“…For the green façade, where the substrates are not on the wall, vegetation is of importance in terms of its acoustic performance. The mechanisms of acoustic dissipation of vegetation have been well summarized by Van Renterghem et al 10 and Prisutova et al 11 (refer to relevant content in the introduction). Generally speaking, leaves and stems are sound absorbing, especially in high frequency range.…”

“…Van Renterghem et al 10 summarized three mechanisms of acoustic absorption from different parts of vegetations: reflection and diffraction by plant elements like leaves, trunks, twigs, and branches; absorption caused by vegetation; destructive interference due to growth media (also referred to as ground effect or ground dip). Prisutova et al 11 explained the mechanisms in different frequency range: thermal dissipation in the lower frequency range (e.g. below 100–200 Hz) 12 ; viscous dissipation in the low and medium frequency (e.g.…”

Effects of vegetation on soundscape of an urban religious precinct: Case study of Myeong-dong cathedral in Seoul

“…5 shows the relative sound pressure levels as functions of source-to-receiver distance in terms of the three different measurement periods: before vegetation covered with soil, one month after, and four years after vegetation. The measurement results show that the relative sound pressure level was the lowest in the before vegetation covered with soil because of the high sound absorption of soils [40][41][42][43]. The sound levels acquired one month after vegetation decrease in a manner similar to those before vegetation covered with soil up to a distance of 10 m from the sound source; however, the difference in sound level attenuation between the two measurement periods becomes larger as the source-to-receiver distance exceeds 15 m, which is attributable to the high absorption coefficient of soil.…”