Distortion is a desirable effect for sound coloration in electric guitar amplifiers and effect processors. At high sound levels, particularly at low frequencies, the loudspeakers used in classic style cabinets are also a source of distortion. This paper presents a case study of measurements and digital modeling of a typical guitar loudspeaker as a real-time audio effect. It demonstrates the complexity of the driver behavior, which cannot be efficiently modeled in true physical detail. A model with linear transfer functions and static nonlinearity characteristics to approximate the measured behavior is derived based upon physical arguments. An efficient method to simulate radiation directivity is also proposed.

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Augmented reality audio (ARA) means mixing the natural sound environment with artificially created sound scenes. This requires that the perception of natural environment has to be preserved as well as possible, unless some modification to it is desired. A basic ARA headset consists of binaural microphones, an amplifier/mixer, and earphones feeding sound to the ear canals. All these components more or less change the perceived sound scene. In this paper we describe an ARA headset, equalization of its response, and particularly the results of a usability study. The usability was tested by subjects wearing the headset for relatively long periods in different environments of their everyday-life conditions. The goal was to find out what works well and what are the problems in lengthened use. It was found that acoustically the headset worked fine in most occasions when equalized individually or generically (averaged over several subjects). The main problems of usage were related to handling inconveniences and special environments.

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