Digital Stethoscope

• Main Author: Muhd Hakim, Azmi
• Published: 2012
• Online Access: http://ir.unikl.edu.my/jspui/handle/123456789/1050

The general purpose of digital stethoscope whether acoustic or digital, is used mainly to listen to heart and lung sounds in the body as an aid to diagnosis. Listening, or auscultation, has been done with acoustic stethoscopes for almost two hundred years; recently, electronic digital stethoscopes have been developed. The goal of a basic digital stethoscope is to have it retain the look and feel of an acoustic stethoscope but to improve listening performance. So for this project is more focus playback and save the result. It will become successful when the system can provide data to visually chart results by connecting to an off-instrument display such as a computer monitor. This advanced functionality increases the physician's diagnostic capability. Maintaining the existing acoustic stethoscope form (i.e., that "look and feel") while improving the performance digitally requires the use of small, low-power solutions. The essential elements of a digital stethoscope are the sound transducer, the audio codec electronics, and the speakers. The sound transducer, which converts sound into an analog voltage, is the most critical piece in the chain. It determines the diagnostic quality of the digital stethoscope and ensures a familiar user experience to those accustomed to acoustic stethoscopes. The analog voltage needs to be conditioned and then converted into a digital signal using an audio analog-to-digital converter (ADC) or audio codec. Some digital stethoscopes have noise cancellation that requires a secondary sound transducer or microphone to record the ambient noise so that it can be removed digitally. In this approach, two audio ADCs are required. Once in the digital domain, a microcontroller unit (MCU) or digital signal processor (DSP) performs signal processing, including ambient noise reduction and filtering, to limit the bandwidth to the range for cardiac or pulmonary listening. The processed digital signal is then converted back to analog by an audio digital-to-analog converter (DAC) or audio codec. Once the captured sound is converted to an analog voltage, it can be sent out through an audio jack and played back vi on either a computer or through the digital stethoscope. The captured sound can also be manipulated digitally. The sound is commonly transferred with a wired interface, such as USB, or with a wireless interface like Bluetooth or another proprietary wireless interface.