A sound system in a room, consisting of single or multiple microphones and loudspeakers connected by an active electrical link, forms a closed loop that may oscillate, or howl, at frequencies for which the magnitude of the loop gain is unity or greater and the phase shift an integral multiple of 2π. This paper gives preliminary results of detailed measurements of 10017 gain and phase, from which howl points can be predicted. The number of howl points versus gain, and the effects of air temperature, room absorption, and transducer configuration on the feedback frequencies are considered. The results have a practical bearing upon techniques of sound‐system equalization.