New measurement technique for ground acoustic impedance in wind farm

Camilla Marie Nyborg, Wen Zhong Shen*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

Ground acoustic impedance is important in the prediction of sound propagation. In this paper, a new measurement technique is developed based on the Image Source method. Two set-ups are used. Set-up 1 consists of a speaker at a height of 0.5 m and two microphones at heights of 0.2 m (or 0.3 m) and 0.5 m with a separation distance of 1.75 m between the speaker and microphones. Set-up 2 has a double separation distance and almost double heights of 0.5 m and 1 m. The impedance measurements were performed at grass-ground and soft soil-ground after harvest in two different wind farms in Denmark. The findings are: (1) The Nordtest method works in Set-up 1, but gives inconsistent results in Set-up 2. (2) The new method gives consistent results in both set-ups. (3) The flow resistivity obtained with an impedance model can only be used with that specific impedance model, and it becomes inaccurate when used with other impedance models. (4) The determination procedure of flow resistivity is suggested to work with any impedance model. (5) A relation between the flow resistivity obtained with the one-parameter model of Delany and Bazley and that obtained with the four-parameter model of Attenborough is derived.
Original languageEnglish
JournalRenewable Energy
Volume164
Pages (from-to)791-803
Number of pages13
ISSN0960-1481
DOIs
Publication statusPublished - 2021

Keywords

  • Wind turbine noise
  • Sound propagation
  • Gound acoustic impedance
  • Impedance measurement

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