Re: Microphone to use for recording internal body sounds?
 

Sennheiser used to make a stethoscope with a microphone for their Auscultation Trolley.

Basically, they took a stethoscope and cut the ear end off and sealed an omni tie mic. in the tube.

So - all you need to do is to buy a doctor's stethoscope and tie microphone.

SO:-
Stethoscope
Sennheiser MKE 2-ew
Sennheiser MZA 900P
CEntrance MicPort Pro

is what you would need to make a stethoscope that would connect to USB.

Re: Microphone to use for recording internal body sounds?
 

Hey guys, thanks for all the responses! Sorry for not being clearer in my original post--this is to be used for diagnostic purposes, so we're really looking to record actual gastro sounds. We'd like to place one mic to record sound from the stomach and at least one mic to record sound from the lower intestines.

When I mistakenly said power board, I meant that we've got a circuit board (https://www.olimex.com/Products/OLin...A13-OLinuXino/) connected to a 12 volt battery power supply. Ideally, the microphones could be connected to the circuit board either via USB or via more typical microphone input, like plugging a mic into a laptop computer (in the latter case, we'd just have to also purchase a couple USB adapters to plug in multiple mics, as our circuit board only has one microphone input and we want to record from 2 or 3 microphones.

Hopefully that clarifies what I'm looking for a little bit. I had seen the previous thread on this topic that Shem linked to and was excited by the ideas posted there, but ultimately couldn't find what I was looking for in any online stores, so was wondering if I was missing something newer to the market. I'll look into what John posted this morning and see if that fits the bill. Thanks!

Re: Microphone to use for recording internal body sounds?
 

The heart sound sensor has an upper cut-off limit of 600Hz, quite low - is this the kind of source frequency response needed for gastro noises? It does occur to me that the on-board mic preamp on the power board you are using probably has enough gain for a headset mic, but probably has a very poor s/n ratio, so an external converter would make sense - however, very few of these mic in, usb out devices have particularly good noise figures and many are very low in gain. I have no idea if things like Lexicon preamps have Linux drivers (I know nothing of Linux as an OS) so if you want to experiment, you need to get something that his low noise and high gain, then you can actually listen properly. There are some useful contact mics on this page.
Cold Gold Contact Microphones - Online Store
Maybe these are worth investigating

Re: Microphone to use for recording internal body sounds?
 

Eric, are you trying to duplicate what the UltraSound techs do? It's more than just baby heartbeats. They do UltraSounds of the abdomen, chest, and even carotid arteries. I've had them all actually performed on me. The sensor has a gel. It helps with picking up those sounds. If listening to regular sounds was adequate for diagnosis, very few ultrasounds would be ordered. The human body is mostly liquid. That's one of the reasons for the ultrasound gel. I used to scuba dive. Sound moving through liquid is very different than what we normally experience.

How are you planning to keep the microphones in place, or is the device to be handheld? Maybe investigate how the UltraSound people do their jobs. The tech is constantly moving the probe, watching the monitor, and listening. I spent thirty years working in Medical Labs. You seem to be trying to reinvent the wheel here. Why not ask people already doing what you are trying to do how they do it?

Don't take this wrong. You did say for Diagnostic Purposes. ARE YOU REALLY SERIOUS WHEN YOU SAY THAT? Will Medical Advice be given based on what your equipment records? Do you have proper licensing and insurance for that? Have you been trained to recognize what you might hear? It's highly regulated by the FDA and other organizations. If you give medical advice... you could be sued, or even arrested. If you are trying to develop a new medical device, that is highly regulated too.

Now if you are a student just working on a science project, well, that's different. Or if you are just recording stethoscope sounds for teaching Nursing Students etc. (already been done, my wife is an RN) at a school or university. That's okay, but you are late getting into it.

What do you mean for diagnostic purposes? Realize also this is a public board, and what you post on the internet... Something harmless can easily be misconstrued. I was fascinated during my visits to the ultrasound dept. as a patient. I invited the techs over to the laboratory and gave them a tour.

Re: Microphone to use for recording internal body sounds?
 

Eric:

Thanks for finally getting back with some clarification. That narrows things down a bit, but also invites many more questions.

I'm wondering why you're using that specific circuit board. Do you hope to have that board analyze the audio in realtime?

Does that board have the capability (speed, drivers, application SW, etc.) of using one or more of the USB inputs as audio inputs? If you don't already have that capability, then (as Paul suggests) you're adding more complexity to your project.

Can you tell us what you are really trying to do here? Not just "connect a microphone to this specific circuit board." More like: "We want to build a device that will use input from two (or more) abdominal microphones and....." Please fill in the blanks, give us some details. We don't need the medical terminology, but it would be helpful if we know what you want to do with these audio signals, whether you need to do them in realtime (as opposed to recording and then post processing them), etc. Perhaps someone will suggest a simpler way to reach your goal.

---

Paul:

Thanks for providing that link. Those are some very interesting products!

Re: Microphone to use for recording internal body sounds?
 

Greg, we're looking to use input from two or more abdominal microphones, record that input, and then analyze them after the recording session to see if we can clearly differentiate the gastro sounds produced at different stages of digestion, such that we could map those sounds and use them to later predict what stage of digestion someone is in based only on the sounds recorded (rather than based on self-report).

And yes, the board has the capability to use USB inputs as audio inputs and record them on an SD card.

Re: Microphone to use for recording internal body sounds?
 

Eric,

Thanks for the further explanation. It sounds as if several of the problems that I envisioned do not exist, if that board is already capable of recording audio through the USB inputs.

Out of curiosity, do you have the Linux version of the board, or the Android version?

And do you already have software that can record multiple audio tracks simultaneously? If so, I'd be curious as to what package that is, as it might be fun for me to play with that board some day.

Anyway, it sounds as if you're at the point of needing just the transducers and the mic > USB converters.

Is this a one-off project? Or do you need to get the components from a vendor that can reliably supply more of them in the near future? (I ask because there are a lot of inexpensive "mic to USB" converters online, but the least expensive are of relatively unknown origin, and the sources may disappear unexpectedly.)

Re: Microphone to use for recording internal body sounds?
 

Linux version, and we'd strongly prefer a reliable vendor to obtain more components in the future.

I'm actually not sure about the software used to record the tracks simultaneously, as a colleague is handling that part. I can find out if it's necessary for finding the right mics, but I believe that it is simultaneous.

Re: Microphone to use for recording internal body sounds?
 

I would suggest that you use an interface that will convert all the mic inputs to a single USB stream, and feed them to your board over a single USB port. That will ensure that all the mics are processed identically (rather than having one processed by the on-board analog input).

I'm sure that there are devices out there that will convert four mics to one USB data stream. However, I've never used one myself, so I'm not going to make any wild guesses and possibly steer you wrong. Hopefully someone else following this thread will have used a four-channel mic-to-USB converter, and can give you a specific recommendation.

Before you get to that point, you will need to identify what transducer you're going to use. Some have unbalanced audio and need "plug in power"; others have balanced audio and need phantom power. The type of transducer needs to match the USB converter. (Converting from "plug in power" to "phantom," or vice-versa, is possible, but doing so would add complexity and cost to your project.)

What you're doing is very specialized. I'd suggest you use the excellent link Paul provided as a starting point. Call the vendor and talk to him about your specific requirements. Hopefully you will then be able to settle on a specific transducer to use for your prototype design. Once you know whether it's "plug in power" or "phantom," you can put the word out and look for a specific mic-to-USB converter.

At some point, you may need a dialog between the manufacturer of your Linux board and the USB converter. The board seems to be fairly new, so you're in uncharted territory. You can hope that everything will work together, but reality might not be that simple.

Also, I feel that some concerns raised previously, by others, are valid. An off-the-shelf mic converter might not have the correct gain, or the correct audio bandwidth, for your unusual application. But you've got to start somewhere for your proof of concept prototype.

As far as the recording software you're using: knowing details at this point won't help me make any specific recommendations for you. But I would like to know it, just for my own information, in case I want to try tinkering and building an audio recorder one of these days.