The effect of purported acoustically transparent materials on sound propagation

It is common practice at large-scale live events to hang materials such as scrim or LED walls in front of sound reinforcement elements. This paper details research into the effect such materials have on sound propagation. A real-life scenario was replicated in a hemi-anechoic chamber where transfer functions were compared before and after the materials were introduced. Incident angle was also examined by adjusting the loudspeaker cabinet angles relative to the primary measurement position. The findings suggest that the purported acoustically transparent LED wall does not actually behave as an acoustically transparent structure; it acts more like a diffuser with a low-pass filter. The scrim, however, did exhibit acoustic transparency for all but the very highest frequencies. The insights gained from this research hold value for manufacturers seeking to enhance the acoustic properties of LED walls and sound engineers interested in optimising sound systems that are required to sit behind such materials.