Stethoscope-type recording system with stretched-in-time playback

Abstract

A system for recording heart sounds from a stethoscope-type device and reproducing selected heartbeats stretched out in time but with the same pitch as recorded. In one embodiment the heart sounds are sampled and converted to a digital representations which are recorded on a tape recorder at a first speed. The tape recorder is of the endless loop recording and playback type. At a signal from the user, the tape recorder plays back at a reduced speed the last few heartbeats which are recorded. These are converted to analog signals and fed back to the transducer in the stethoscope for reproduction as natural heartbeat sounds merely stretched in time. Another system records the heartbeat sounds on a rotating recorder such as a magnetic drum. The magnetic transducer may be driven at variable speeds so that, when activated by the user, the speed of the playback transducer is reduced relative to the speed of the transducer during recording, without reducing the rotational speed of the drum. Thus, the pitch of the heart sounds is not affected, although they are stretched out in time. Another embodiment utilizes a delay line for temporary storage with scanning of selected taps in the delay line for storage of selected samples in the memory. Upon activation by the user, the stored samples in the memory are read out at a reduced rate, filtered for smoothing, and fed back to the stethoscope transducer for reproduction as stretched heartbeat signals at the original pitch.