Microphone to use for recording internal body sounds?
 

I'm part of a group working on a device to record internal body sounds, such as gastrointestinal sounds, but we're having difficulty finding an appropriate microphone to use. We'd prefer something that can plug into our power board via USB or something similar to this design (Heart Sound Sensor [SEN42771M] - $59.00 : Seeed Studio Bazaar, Boost ideas, extend the reach), but haven't found anything currently available for sale.

Any advice that could be offered would be a huge help. I'm not an audio expert at all, but this seemed like the right place to go based on similar threads I've seen from the past. Thanks!

Re: Microphone to use for recording internal body sounds?
 

Hi Eric, welcome to DVi.

Have you thought about using a digital recording stethoscope, such as Digital Stethoscope | ADInstruments

Re: Microphone to use for recording internal body sounds?
 

Yes, we were originally considering using a digital stethoscope, but have had difficulty getting those microphones to hook up and work with our program, so I was wondering if there might be a better alternative. That said, is there an easy way to take the input from a digital stethoscope and connect it via USB? If so, we might still be able to make it work.

Re: Microphone to use for recording internal body sounds?
 

Eric, First welcome to DVi...I'm sure someone will come up with something for you. We've got some of the best talent in the world here.
By the same token I have to say when I read your post I almost had to laugh because the picture that immediately came into my head was someone swallowing a Sanken COS-11D or a Countryman B6 with the tail hanging out of their mouth hooked up to a wireless mic pak. I'm really sorry but that's what hit my head as my stomach was making enough noise to be recorded without the use of any microphone. Please forgive my sense of humor I really do apolgize. I'm pretty sure someone who is a lot more audio tech savvy than I will respond. Once again Welcome and good luck.

Re: Microphone to use for recording internal body sounds?
 

I'm wondering if some sort of specialized PZM mic might be the way to go... or maybe I'm way off track?

Re: Microphone to use for recording internal body sounds?
 

Welcome!

First of all, what do you mean by "power board"? In my mind, that would be the disconnect panel where commercial line voltage comes into the building... I doubt you want to connect the mic to that.

Do you mean an audio mixing board? If so, does it have balanced inputs, and if so do they have phantom power? Or is it some sort of consumer board with unbalanced inputs, and if so do they have "plug in power"?

And what is a digital mic? A mic is an analog device that converts analog changes in air pressure to an analog voltage, so most simply the output is analog. Having said that, some mics incorporate some digital electronics to convert the mic signal, usually, to USB format. In that case, you can't connect it to an analog mixing board, but rather you need to connect it to a computer's USB input.

BTW, the "Digital Stethoscope" is very specialized. It appears to be a [analog] microphone in a stethoscope bell, combined with some digital processing to somewhat "clarify" the sound, and then analog outputs again which presumably can be recorded on a normal audio recorder. (But the description at the linked website is not entirely clear about this.)

And what sort of internal body sounds are you hoping to capture, out of curiosity? Something specific, or all body sounds? The nature and frequency range of the sound(s) could be very relevant to your question.

Please try to define more clearly what you already have -- make & model number would be helpful -- and we can give you some more specific solutions!

Re: Microphone to use for recording internal body sounds?
 

There is an existing thread on a similar topic
http://www.dvinfo.net/forum/all-thin...lp-please.html

What mic you use depends on the end use of the sound: audio for documentary or drama; or interpretive for diagnostics. From where I understand things,it is a case of making or modifying a USB mic or other to get good skin (or perhaps bone ) contact .

Re: Microphone to use for recording internal body sounds?
 

Thanks for pointing out that other thread, Shem -- much appreciated!

Re: Microphone to use for recording internal body sounds?
 

Eric, I think you're coming at this from the wrong end, nope I don't mean that :)

Whatever you record with a body mic won't sound like you imagine it, it won't be good enough. It's got to be 'animated', sound 'internal'
and be quickly recognised by your listeners.

So use your imagination. Slowing the recorded speeds of sounds is my first thought.

Get short lengths of plastic tubes, each with a different diameter. Fill a big bucket with water, a wide brim bucket in a very quiet room < very important.

Blow bubbles and record them, fast and slow. The more you do the better you'll get, try the tubes at different depths in the bucket.
The aim is to slow down the best of them.

Flush toilets and record water gurgling down various drains. Load them to your NLE at different speeds. Add various explosions and lions growling
at speeds and mix to taste.

We did the Whale Exhibition for the Australian Museum like this, a whole floor as an undersea location, including the lighting.
All various blue hues, with slow rotating coloured lights. Huge woofers playing 24 track whale/bubble/growling sounds, with giant skeletons.
My satisfaction was watching the wide eyed school kids, I tell you there is nothing like it :)

Cheers.

Re: Microphone to use for recording internal body sounds?
 

I was assuming, from the way the OP phrased his question, that he wants to record authentic internal body sounds, perhaps for diagnostic or instructional purposes.

Re: Microphone to use for recording internal body sounds?
 

Yes Greg, but either way, I think you've got to animate it, like Hollywood does, larger than life to get the point across.

Cheers.

Re: Microphone to use for recording internal body sounds?
 

But not if he's using the recording to train medical students about how the body should actually sound. If they're learning how a heart should sound on their stethoscope, you don't want them listening to a slowed-down toilet flush!

Re: Microphone to use for recording internal body sounds?
 

In that case I'd recommend using Stethoscopes. No offence Greg, but I think you've missed the point of my post 9. Indeed Eric might want a mic
for this job, but those were my recommendations.

Cheers.

Re: Microphone to use for recording internal body sounds?
 

No Allan, I don't think I missed your point. If I understand you correctly, you were saying that for a "show biz" use, artificial sounds might be more "dramatic" or "impressive" than the real thing, viz a viz your "wide eyed school kids." I certainly don't have any argument with that.

My point was simply that if the intent is to use the recording for something serious like medical training, then I think a realistic recording would be more appropriate than manufactured sound effects.

Since the OP said "record internal bodily sounds," rather than "produce bodily sound effects" I assumed he was after realistic audio. And, indeed, one device the OP looked at was modeled on a normal stethoscope; that simply reinforced my belief that he's after a realistic recording of the actual bodily sound.

But for your school kids, I'm sure slowed-down bubbles are great.

Re: Microphone to use for recording internal body sounds?
 

Even though Eric doesn't specify what he will be using the sounds for I also read that he wants the real stuff, if he would have said he was doing a horror movie or a episode of house then I could understand you could use your imagination but if he needs the material to use in med school for educational purpose then I can understand Greg's point about the toilet sounds :)

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.