Stethoscopes have long been used by physicians to monitor auscultatory sounds. Typically stethoscopes have been comprised of a head or chestpiece, a sound transmission mechanism and an earpiece assembly. The chestpiece is adapted to be placed near or against the skin, body, of a patient for gathering the auscultatory sounds. The sound transmission mechanism transmits the gathered sound to an earpiece, or a pair of earpieces called a binaural earpiece, where the physician or other health professional may monitor the sound.
Recently, some stethoscopes have utilized electronics for at least part of the sound processing path. In most of these devices, the auditory sound is picked up by a microphone usually located in a detection device which is similar to the chestpiece of a conventional acoustic stethoscope in external appearance. The electrical signal from the microphone is then processed electronically and is coupled to a speaker, or speakers, where the electrical signal is converted back into an auditory sound for reception by the physician. Of course, other electronic analysis or display of the auscultatory sounds may be performed by the signal processor, in addition to the usual conversion back into an auditory sound.
The incorporation of electronic circuitry into the stethoscope has been a considerable design problem for the engineer. Typically, the electronic circuitry increases the physical size of the stethoscope package. Either the size of the chestpiece is increased in size dramatically or an additional enclosure to house the electronics is located between the chestpiece and earpiece assembly or both. In both of these cases, the resulting stethoscope is bulky, cumbersome to use and not easily storable between uses.
Further, the location of and housing of the electrical to acoustic transducer, or speaker, in the electronic stethoscope is a problem.
In one case, the speaker may be located in the chestpiece. In this case, the acoustic signal must then be routed through long tubes to eventually reach the user's ears. The physical distance which this acoustic signal must travel increases the amplification burden of the electronic stethoscope and increases the probability of contamination with unwanted and non-pertinent sounds.
In another case, the speaker may be located in either a separate housing or otherwise contained within tubular members near the user's ears. The advantage of this technique is to decrease the amount of amplification required and to decrease the likelihood of noise contamination. However, the disadvantage to this technique is that a severe acoustic restraint is placed on the speaker housing and/or a separate speaker must be used for each earpiece. Both of these items significantly limit the useability of the electronic stethoscope.
U.S. Pat. No. 3,790,712, Andries, Electronic Stethoscope System, describes an electronic stethoscope which has a chestpiece sized and shaped like a large rectangular, box which houses the electronic circuitry of the stethoscope. The box has a projecting member with a forward lip portion for engagement with a skin surface. A speaker is positioned in a housing located at the juncture of separate earpiece tubes. The housing in which the speaker is positioned is acoustically sealed from an electrical cord which electrically and mechanically couples the speaker housing to chestpiece (detection device).
U.S. Pat. No. 4,071,694, Pfeiffer, Stethoscope, describes a stethoscope which has both an electronic and an acoustic capability. The chestpiece of the stethoscope has a conventional shape and achieves a conventional function. A speaker/receiver is located at the bifurcation of the earpiece tubes and is connected by wires integral to the sound tube. This is a combination electronic-acoustic device thus the speaker is mounted to provide a bypass channel for sound under the purely acoustic mode of operation. The compartment containing the speaker/receiver is acoustically sealed from the flexible conduit coupling the speaker/receiver to the chestpiece.
U.S. Pat. No. 4,170,717, Walshe, Electronic Stethoscope, describes an electronic stethoscope which has a chestpiece having an elongated housing carrying a body piece which includes an annular ring to be placed against a patient's body. An electrical cord couples the chestpiece to a speaker positioned in a housing. The acoustic output of the speaker is coupled to a length of single tubing which, in turn, connects to a conventional binaural earpiece assembly.
U.S. Pat. No. 4,254,302, Walshe, Electronic Stethoscope, describes an electronic stethoscope having a chestpiece for acquiring auscultatory sounds from the body of a patient. A microphone for sound pickup and electronic signal processing equipment are located in the chestpiece. A flexible duct enclosing an electrical wire connects the chestpiece to an enclosure containing a small speaker. The speaker is acoustically isolated from the interior of the flexible duct connecting the speaker enclosure with the chestpiece. Another flexible duct of a specified length "h" acoustically couples the output of the speaker to a binaural earpiece assembly.
U.S. Pat. No. 4,723,555, Shue, Multi-Functional Radio/Wire Stethoscope Apparatus, and U.S. Pat. No. 4,878,501, Shue, Multi-Functional Radio/Wire Stethoscope Apparatus, describe an electronic stethoscope which has a chestpiece with a diaphragm on one side and a bell on the other designed for gathering visceral sounds. The electrical signal is provided to a wireless transmitter or to a speaker/earphone jack.
French Published Patent Application No. 2,659,007, Oclin et al, Stethoscope With Electronic Amplification, describes a stethoscope having [with] a microphone located in one sealed cavity and having a loudspeaker located in a second sealed cavity. The sealed cavity containing the loudspeaker is connected to the first sealed cavity containing the microphone by an electric conductor. The output of the loudspeaker acoustically communicates to a binaural earpiece.