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.