Three popular stethoscopes were used in this study: a nonamplified stethoscope (Littmann Classic S.E. This study did not include a newer amplified stethoscope that is popular among health professionals with hearing loss (i.e., Thinklabs One digital stethoscope) because it requires the use of earphones or headphones as the stethoscope tube, and thus differences in the audio quality between earphones/headphones may affect the acoustic measurement of the stethoscope. This study aimed to evaluate the acoustics of three stethoscopes (nonamplified and amplified stethoscopes) for three different digitized heart sounds: normal, aortic valvular stenosis (AVS) and pulmonic valvular stenosis (PVS). Although frequencies of normal and abnormal heart sounds were previously reported, the acoustic analyses of the frequency responses of conventional and amplified stethoscopes to different heart sounds have not been clearly described. Other cardiac and pulmonary sounds, such as murmurs, ejection clicks and crackles, occur at <300 Hz. Spencer and Pennington indicated that S1 and S2 occur between 50 and 500 Hz, while S3 and S4 occur between 20 and 200 Hz and S3 appearing at the lowest frequency. In fact, heart sounds have multiple components with S1 and S2 being normal, S3 being normal or pathologic and S4 almost always being pathologic. The bandwidth of cardiopulmonary auscultation is between Hz. Noland showed that the best frequency range for diagnosing the most critical heart sounds is between 70 and 120 Hz. stated that the heart sounds fall between 20 and 650 Hz and are better detected by the bell of a stethoscope. Spencer and Pennington reported that normal lung sounds range from 100 to 1000 Hz. For example, the frequency range most critical in diagnosing lung sounds is between 200 and 600 Hz but no higher than 2000 Hz. It should also be noted that each body sound varies widely in terms of frequency range. Unsurprisingly, the acoustical characteristics of stethoscopes have shown different results, particularly when stethoscopes were measured in an ideal setting without much ambient noise. The literature is replete with studies on stethoscopes (both electronic and conventional) but varies widely in design and analysis methods. Moreover, specifications for amplified stethoscopes are affected by factors such as the variability of degree and configurations of unaided hearing loss among health professionals, various coupling methods to personal hearing devices (e.g., hearing aids and auditory implantable devices) and the inability of clinical audiologists to assess calibrated audiometer frequencies <125 Hz (in some cases, 250 Hz). Unfortunately, these claims cannot be assumed to be uniformly distributed across frequencies. Although electronic stethoscopes provide specifications, consumers must rely on the individual claims made by manufacturers regarding gain (dB) and frequency (Hz). 974), and this currently remains the case. stated >20 years ago that “stethoscopes are rarely tested, rated, or compared and are often chosen for their appearance, reputation, and inadequately supported claims of performance” (p. Currently, no standards (or parameters) exist for measuring the acoustical characteristics of stethoscopes. Stethoscopes can be categorized into two categories: electronic (also called amplified or digital) and conventional (also called nonamplified or acoustic) stethoscopes.Īmplified stethoscopes were designed to overcome the auditory limitations of nonamplified stethoscopes in terms of amplifying sounds, eradicating background noise and filtering sound frequencies. Appropriate diagnosis of diseases, such as cardiovascular disease, using a stethoscope depends on the experience and the hearing threshold of health professionals and the acoustic parameters of the stethoscope. Stethoscopes are acoustic devices used to listen to sounds of the body including those from the lung, heart, gastrointestinal tract and blood flow in arteries and veins. Hearing loss affects 466 million people globally including health practitioners, who routinely require using stethoscopes for physical examination.
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