Microphone that can detect wheezing sound from the chest

[choyelise]

Hi all!

I am searching of types of microphone/disc that can detect wheezing sound from the chest area but I am totally clueless of what type of microphones to use. Also, there should be less noise when picking up the signal. Currently I am using a piezo disc, but that could not detect the wheezing sounds from the chest only heartbeat.

Anyone can help me?

Thanks a lot!

 

[Algr]

Does the sound of a wheezing chest actually emanate from the chest? Putting the mike by the mouth (to the side, not in the path of breath) might be more effective.

 

[Bobbywhy]

choyelise, It is often useful to search for how others accomplish the same signal detection with microphones that you’ve asked about. For your information, typically detected wheezing sounds are passed through a band pass filter, spanning from 100 Hz to 3,000 Hz, for example. From a frequency perspective, wheeze is associated with spectral peaks that last for a minimal period of 80 milliseconds. Often a Short Time Fourier Transform of the filtered sound is performed to isolate and display the wheeze signal.

Using these search terms (acoustic sensors for lung sounds), (acoustic lung imaging), and (auscultation) in Google search I found the following information:

Sensors for Lung Sound Recording
Two types of transducers are in common use for lung sound recording and research: the electret microphone with coupling chamber and the accelerometer (9). Small electret microphones are widely available for speech and music recording. When coupled to the skin by a sealed chamber, similar to a stethoscope bell, this type of microphone is a sensitive lung sound transducer. Different sizes and shapes of coupling chambers have been found to affect the overall frequency response of this coupling. Those arrangements with smaller, conically shaped chambers are more sensitive to higher lung sound frequencies (10, 11), but also highly susceptible to ambient noise. Contact accelerometers are also popular in lung sound research and can be calibrated on a vibration table so their output is quantified. However, they are typically more expensive than electret microphones, are often fragile, and may exhibit internal resonances near the lung sound frequencies of interest.
10. Wodicka G. R., Kraman S. S., Zenk G. M., Pasterkamp H.Measurement of respiratory acoustic signals: effect of microphone air cavity depth. Chest 1994;106:1140–1144. [CrossRef] [Medline]
11. Kraman S. S., Wodicka G. R., Oh Y., Pasterkamp H.Measurement of respiratory acoustic signals: effect of microphone air cavity width, shape and venting. Chest 1995;108:1004–1008. [CrossRef] [Medline]
http://www.atsjournals.org/doi/full/10.1164/ajrccm.156.3.9701115

Acoustic detection of respiratory conditions
United States Patent 6443907
Abstract: Diagnostic techniques are provided to enable the detection of a respiratory condition within a patient's body. The diagnostic techniques compare the acoustic generation and transmission characteristics of the patient's chest and lungs to reference acoustic characteristics and/or predetermined threshold values to determine if an abnormal respiratory condition is present within the patient. The diagnostic techniques process sound waves or vibrations that have interacted with a respiratory condition within a patient and which impinge on the chest wall of the patient. The sound waves or vibrations may be initiated by a speaker that emits sounds waves into the mouth and trachea of the patient or may be indigenous sounds. Alternatively, the sounds waves or vibrations may be initiated using percussive inputs to the chest wall of the patient. In processing the sound waves, the diagnostic techniques calculate energy ratios using energy values within high and low frequency bands, signal time delays, and/or dominant frequencies and compare the calculated values to predetermined reference thresholds to generate outputs indicative of the respiratory condition within the patient.
http://www.freepatentsonline.com/6443907.html

The VRIxp System (Deep Breeze, Or-Akiva, Israel) is a computer based acoustic lung imaging system, developed to acquire, quantify, monitor and store breath sounds, and has been described in detail elsewhere.14 15 Briefly, the system hardware is composed of 40 active piezoelectric contact sensors and two inactive contact sensors (lateral sensor on first row of each array) (Meditron ASA, Oslo, Norway) with a linear frequency response of ±2 db in the frequency range of 50–400 Hz; sensors are assembled on two planar arrays. Contact of the sensors with the chest wall is maintained by an open system with a constant, computer controlled low vacuum (that in bench trials (data not shown) has been demonstrated not to interfere with lung sound detection). Lung sounds, recorded during 12 s of tidal breathing, are converted to digital data by a 64 multi-channel analogue to digital conversion system (16 bit) with a sampling rate of 19.2 kHz. Inspiratory and expiratory signals are analysed separately. The digitised sounds are band pass filtered between 150 and 250 Hz to reduce interference generated by chest wall movement and heart sounds.
14. Dellinger RP, Parrillo JE, Kushnir A, et al. Dynamic visualization of lung sounds with a vibration response device: A case series. Respiration 2008;75:60–72. [PubMed]
15. Dellinger RP, Jean S, Cinel I, et al. Regional distribution of acoustic-based lung vibration as a function of mechanical ventilation mode. Crit Care 2007;11:R26. [PMC free article] [PubMed]
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2571960/

Clinical Policy Bulletin:
Computerized Wheeze Detectors
The PulmoTrack, or WIM-PC (KarmelSonix, Ltd), http://www.accessdata.fda.gov/cdrh_docs/pdf/K980878.pdf

The Personal Wheezometer (KarmelSonix, Ltd) The PERSONAL WHEEZOMETERTm (PW) is intended to be a
home use version of the PulnmoTrackg (K980878) and PulmoTrack
model 2010 (WIM-PC) (k071955), providing wheeze-rate
information for both home and clinical settings.
The VRlxp (Deep Breeze, Ltd)

http://www.aetna.com/cpb/medical/data/800_899/0813.html

http://www.isoneamed.com/wheezometer.html