The advent and subsequent development of Concorde required answers to questions relating to the human responses of communities exposed to the sonic booms of aircraft flying at supersonic speeds.

The study of such subjective reactions under laboratory conditions required facilities able to reproduce the classical N-pressure wave of the sonic boom to subjects listening not only through headphones but also under the more realistic circumstances of whole body exposure within an enclosed pressure booth. The electro-mechanical reproduction of N-waveforms having rise-times and decay durations of 1-10ms and 50-100ms respectively was no mean feat. Eric Zepler successfully applied his electronic skills to the successful development of both of these facilities which enabled many students to complete their higher degrees.

The headphone research enabled the formulation of theoretical models for the calculation of the loudness level of sonic booms from their pressure-time functions. The pressure booth allowed the simulation of a sonic boom under free-field conditions. The underlying principle was that loudspeakers built into the wall of the pressure-tight booth acted as pistons so allowing the faithful reproduction of N-waves. This was not an easy task as the mechanical impedance of a loudspeaker causes the waveform displacement to be different from the applied force, and Eric Zepler used electro-mechanical analogies to model the required responses of the loudspeaker coil so ensuring the correct outputs.

Eric Zepler also personally experienced the effects of the sonic boom at first hand when being overflown by military fighter aircraft during an ISVR team visit to Meppen in West Germany in 1969 to measure the acoustic and structurally induced vibration effects. He was invaluable on that occasion because he was able to interview members of the local population in order to obtain their subjective reactions at first hand.