DIN6 Medical Heart Sound Cardio Microphone with XLR?

Discussion in 'Accessories / Connections' started by Jimi du Belle, Oct 24, 2014.

  1. DonnyThompson

    DonnyThompson Distinguished Member

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    Location:
    Akron/Cleveland, OH
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    To be clear, I'm not trying to sabotage the part of this thread in which modifications are being discussed, which was how to modify the element that Jimi has...

    To the contrary, I think it's great when smart minds get together and talk about possibilities. But, since I can't contribute to that end of things, I thought I would at least address the original goal, which was to record heart beats. I think there's likely an easier (and probably better) way to accomplish this task, other than trying to modify an older device... but ...that doesn't mean that I think that this modification shouldn't be discussed... I absolutely do think that it should be talked about, because it's a cool technical concept, and, because we have members like Boswell and MrEase, who are really smart guys.

    I'm positive that there is much to be learned, and the only way to learn is to discuss these things.

    We all work in a craft where it's absolutely essential to have guys just like Bos and Ease - who not only have the technical knowledge, but who also have the creative mindset to say "hmmm, okay, so, what if...?"

    IMHO of course. ;)

    d.
     
  2. MrEase

    MrEase Active Member

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    Jan 19, 2006
    Location:
    West Suss ex, UK
    Well I'm amused by my own thoughts of what colleagues would make of me being accused of "modern thinking"! Sarcasm would abound! ;<)

    I think the point is (taking into account later posts too) that the OP has a transducer designed for the purpose, no matter how old it is. The concept is indeed very simple and I have not been thinking in terms of fidelity but rather, as the frequencies involved are low, that it is sensible to preserve the lows by using a high impedance buffer. As Boswell said, a high impedance DI box could be perfectly adequate or even a high impedance "instrument" input on a soundcard.

    Rather than trying to reinvent the wheel I think it would be sensible to use the transducer specifically designed for the job and it should not be too difficult to achieve. Whilst it would indeed be possible to superimpose a DC supply voltage, my earlier point was that this could not be achieved on a single conductor given the load impedance required. There is no way to provide sufficient power for a buffer, hence the deduction that the transistor cannot realistically be in the transducer itself. This is again just simple engineering.

    BTW, thanks Donny for the kind words. In a way that's why I chose the tag "Mysteries" as I hope to dispel some of the myths that surround the engineering involved in our chosen field.
     
  3. Jimi du Belle

    Jimi du Belle Active Member

    Joined:
    Oct 24, 2014
    Location:
    Germany
    Thank you for all your answers. It's been a while and I have progressed a little:
    I now made myself a simple stethoscope mic with a cheap stethoscope and an simple small speech mic with a tiny preamp. I put the mic in the "sound channel" of the stethoscope and that's it. The results are acceptable. But still I'm not satisfied with the quality.
    I will try to get hold of a DI box to go back experimenting on the RFT Herzschallmikrofon.
    Currently there is a passive DI box available for me, I'll try that one first and will tell you my results next week.
    If that does not work out I will try to get hold of an active DI box.
     
  4. DonnyThompson

    DonnyThompson Distinguished Member

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    Akron/Cleveland, OH
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    Thank you for being courteous and giving us an update. Not everyone who visits RO seeking help does this ... in fact, hardly any ever do, so thanks for taking the time to do so.

    :)

    We need more guys like you. ;)

    Moderating the posts here isn't only about looking for inappropriate behavior - it's also searching for people/posts giving inaccurate information.

    When someone posts here on RO, it doesn't just stay here... it goes out to the world; and if someone else may be searching the internet for an answer to a particular problem or scenario, they don't always get accurate information; in fact, there's probably a greater chance of receiving wrong information than there is finding the right information. There's far too much myth and BS floating around out there already about audio and acoustics; and while we can't control what is posted on other sites, we can control it here.

    So having cats like you around to give accurate info is absolutely essential. Thanks. ;)

    -d.
     
  5. Jimi du Belle

    Jimi du Belle Active Member

    Joined:
    Oct 24, 2014
    Location:
    Germany
    Back for a thread revival:

    I have found a german artist recording heart sound with a very special phonokardiograph:
    02_kontrapunkt.jpg
    project page: http://ingoguettler.de/kontrapunkt/

    It is a metall housing held by two feet. Screwed into the capsule/housing is a red kind of pestle (replaceable). Seems like you put the whole thing on the chest with its two feet and the third red pestle to record the heart sounds…

    Does anybody have any idea what it is exactly and where one can get hold of one or DIY?
     
  6. Boswell

    Boswell Moderator Distinguished Member

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    The last time I saw one like that it had a 78rpm piezo pickup cartridge inside, along with crude mechanical limit stops. It was not a pleasant item to deal with, but it did work, and it went down to d.c.!
     
  7. MrEase

    MrEase Active Member

    Joined:
    Jan 19, 2006
    Location:
    West Suss ex, UK
    I can't say I've ever seen anything like this before. What worries me is that the gear seems to have produced a sonic boom that has blown a hole straight through to the library! :) What happened to those previously sitting on the chairs is anyone's guess....
     
    dvdhawk likes this.

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