Development of a low-cost electronic stethoscope - DIY Digital Stethoscope

Auscultation while wearing PPE (especially coveralls), using traditional stethoscopes is often not feasible. While some commercially electronic stethoscopes can circumvent this problem by playing audio using headphones over/ inside PPE, the currently available ones are too costly. We plugged an electret microphone into earpiece of a stethoscope and through various audio processing algorithms improved the audio quality. We packaged these processes into an app, freely available for download from Google Play Store. Audio quality through this device is at least equivalent to the one heard through traditional stethoscopes. We are validating the device in pediatric and adult clinical setup.

Color Spectrographic Analysis of Respiratory Sounds: A Promising Technology for Respiratory Monitoring

Background: The need for reliable respiratory monitoring has increased in recent years with the frequent use of opioids for perioperative pain management as well as a high prevalence of patients suffering from respiratory comorbidities. Objective: Motivated by the success of acoustical color spectrographic techniques in other knowledge domains, we sought to build proof-of-concept systems for the computer-based color spectrographic analysis of respiratory sounds, recorded from various sites. Methods: We used a USB miniature electret microphone and a Windows-based color spectrographic analysis package to obtain color spectrograms for breath sound recordings from the neck, from an oxygen mask, from the ear canal, and from a leak-free microphone pneumatically connected to the cuff of a laryngeal mask airway. Results: Potentially useful color spectrographic displays were obtained from all four recording sites, although the spectrograms obtained varied in their characteristics. It was also found that obtaining high-quality color spectrograms requires attention to a number of technical details. Conclusion: Color spectrographic analysis of respiratory sounds is a promising future technology for respiratory monitoring.

Design and Implementation of Embedded Audio System based on Zynq-SOC

Nowadays smart world requires, Embedded audio system with optimum design metrics for smart applications in various fields like smart car, intelligent systems and Robotics etc. This paper describes the Design and implementation of embedded Audio system for real-time applications on SOC-FPGA with optimized design metrics (low power, low-cost, low development time, low area, high speed). An electret microphone / line in are used to feed the audio input. An audio codec from Analog devices named ADAU1761 which is integrated on the zynq-7020 board. In the proposed embedded audio system, the block design in Vivado2017.2 has been modeled with VHDL; application software developed using C language in SDK2017.2. This Audio system is the optimized solution for a wide range of smart applications.

Color spectrographic respiratory monitoring from the external ear canal

The need for simple and reliable means of respiratory monitoring has existed since the beginnings of medicine. In the present study, we describe the use of color spectrographic analysis of breathing sounds recorded from the external ear canal as a candidate technology to meet this need. A miniature electret microphone was modified with the addition of an adapter to allow it to be placed comfortably in the external ear canal. The amplified signal was then connected to a real-time color spectrogram program running on a laptop personal computer utilizing the Windows operating system. Based on the results obtained, we hypothesize that the real-time display of color spectrogram breathing patterns locally or at a central monitoring station may turn out to be a useful means of respiratory monitoring in patients at increased risk of respiratory depression or other respiratory problems. Finally, we conducted a statistical analysis that suggests that significant spectrogram differences may exist among some groups investigated in the study.

Use of Ultrasonic and Audio Signals to Monitor Temperature in Stratospheric Balloons

For gas temperature measurements in stratospheric balloons, traditional methods of measuring gas temperature do not work well due to radiant heating and insufficient heat transfer. To measure the gas temperature several methods of acoustic temperature measurement are being developed. One of these methods is the pitch catch method. A perceived distance pitch catch method using an ultrasonic distance sensor was proposed and tested. However, at low pressures the density of air is too low to allow sound to propagate well. This means that at a certain pressure, the ultrasonic distance sensor will not receive a reflected sound with sufficient amplitude to calculate the apparent distance accurately. Tests were conducted in a high altitude chamber to determine the accuracy of temperature measurements and the fail pressure. It was determined that the optimum configuration for this device would not allow it to function at a sufficient altitude nor give the temperature accuracy required. An alternative timing method using a piezo speaker, electret microphone, and time of flight measurements was explored. The timing method achieved a detectable signal down to 1.0kPa. Further work is being done on the timing method to increase the accuracy of the device.

Silicon micro-levers and a multilayer graphene membrane studied via laser photoacoustic detection

Laser photoacoustic spectroscopy (PAS) is a method that utilizes the sensing of the pressure waves that emerge upon the absorption of radiation by absorbing species. The use of the conventional electret microphone as a pressure sensor has already reached its limit, and a new type of microphone – an optical microphone – has been suggested to increase the sensitivity of this method. The movement of a micro-lever or a membrane is sensed via a reflected beam of light, which falls onto a position-sensing detector. The use of one micro-lever as a pressure sensor in the form of a silicon cantilever has already enhanced the sensitivity of laser PAS. Herein, we test two types of home-made sensing elements – four coupled silicon micro-levers and a multilayer graphene membrane – which have the potential to enhance this sensitivity further. Graphene sheets possess outstanding electromechanical properties and demonstrate impressive sensitivity as mass detectors. Their mechanical properties make them suitable for use as micro-/nano-levers or membranes, which could function as extremely sensitive pressure sensors. Graphene sheets were prepared from multilayer graphene through the micromechanical cleavage of basal plane highly ordered pyrolytic graphite. Multilayer graphene sheets (thickness ∼102 nm) were then mounted on an additional glass window in a cuvette for PAS. The movements of the sheets induced by acoustic waves were measured using an He–Ne laser beam reflected from the sheets onto a quadrant detector. A discretely tunable CO2 laser was used as the source of radiation energy for the laser PAS experiments. Sensitivity testing of the investigated sensing elements was performed with the aid of concentration standards and a mixing arrangement in a flow regime. The combination of sensitive microphones and micromechanical/nanomechanical elements with laser techniques offers a method for the study and development of new, reliable and highly sensitive chemical sensing systems. To our knowledge, we have produced the first demonstration of the feasibility of using four coupled silicon micro-levers and graphene membranes in an optical microphone for PAS. Although the sensitivity thus far remains inferior to that of the commercial electret microphone (with an S / N ratio that is 5 times lower), further improvement is expected to be achieved by adjusting the micro-levers and membrane elements, the photoacoustic system and the position detector.

Design and Experiment Study for Acquisition System of the Children Lung Sound Signal

Lung sound contains a wealth of information on organ function and pulmonary physiology and pathology status information, and lung sounds auscultation has become a useful clinical tool in the diagnosis of lung disease. Therefore, lung sound acquisition system is designed using STM32 microcontroller as the master chip. The system uses a stethoscope and electret microphone with signal processing circuit and system flow chart is also given. Finally related experiments is done based on designed system, the results show that: the design of the system can stabilize unmistakable signal acquisition lung sounds.

Low Distortion Analog Front-End for Digital Electret Microphone

This paper presents a low distortion analog front-end (AFE) circuit to process electret microphone output signal. A source follower is employed for the input buffer to interface electret microphone directly to the IC with level shifting. A single-ended to differential converter with output common-mode control is presented to compensate the common-mode variation resulted from gate to source voltage variation in the source follower. A replica stage is adopted to control the output bias voltage of the single-ended to differential converter. The prototype AFE circuit fabricated in a 0.35μm CMOS technology achieves 68.2dB peak SNDR and 79.9dB SFDR over an audio signal bandwidth of 20kHz with 2.5V supply while consuming 1.05mW.