Acoustics test. Technician holds a microphone behind a plexiglass panel to test its sound reflective properties. Sound is being broadcast at the front of the panel, and the microphone is picking up the amount it allows through. This panel is designed for use in a large concert hall to provide an even sound throughout the hall. This is important as otherwise the audience at the rear of the hall would receive poorer sound quality than those at the front. All such acoustic research is carried out in an anechoic chamber, where the walls are covered in material which prevents any reflections from disturbing the readings.