Effects of turbulent flow characteristics on wind-induced noise generation in shielded microphones

Outdoor noise measurements can be highly affected by the wind-induced noise generated by turbulence structures present in the flow and wakes generated at the air and windshield interface. Various commercially available windshields were tested in a small anechoic wind tunnel in order to investigate the effects of turbulent flow properties on the wind-induced noise in shielded microphones. To distinguish the contribution of wind-induced noise from the acoustic signal an Incoherent Output Power analysis between two microphone signals has been used. The effects of mean flow velocity, turbulence intensity and average length scales on the wind-induced noise in shielded microphones were evaluated. An incremental trend with increasing airflow velocity has been found for the wind noise spectral amplitudes. The findings indicate a dependency between turbulent scales and the wind-induced noise levels at low frequencies. The overall wind-induced noise was found to be insensitive to the incoming flow turbulence intensity levels which may suggest that other parameters of the incoming flow turbulence, such as turbulence scale, are more important for the processes of wind-induced noise generation.