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  1. Hi,
    I have been experiencing occasional, loud static sounds in my recordings using Sennheiser ew 100 g3 set, coupled with a Zoom H4n.
    The Sennheiser lavalier mic is clipped on around the speaker's neck and the transmitter part is either hand-held, in a pocket, or hanging from the belt, while the receiver is attached to Zoom H4n.

    I recently recorded about 22 presentations this way and a few of them have this static noise that I cannot explain. I had the same problem last year and I couldn't figure out why. I changed frequencies thinking perhaps some electronic device interfered, but it did not solve the problem.
    I end up having to go through all the videos and find a way to cut out the noise if it's not in the middle of a word, or find a way to reduce it.

    I am attaching two samples to help me explain better.


    Any ideas how I end up getting this problem?

    Thanks
    Image Attached Files
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  2. You're getting distortion from over-modulating. In other words, turn down the record volume.
    edit: check your transmitter volume first.
    Last edited by smrpix; 4th Nov 2015 at 12:31.
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  3. i had a brief look at what over-modulation is. Even though it seems to be a bit different from clipping, it sounds like it happens when the transmitted volume is too high. However, when I look at the waveforms of this noise in my videos, it's not necessarily too loud, they do not reach to 0dB; the distorted noise happens even when the audio being recorded is not loud; it happens when someone is speaking as well as when the person is between sentences. Am I right?

    I just checked my transmitter sensitivity. It's at -9dB.

    Anything else I can look into?
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  4. Originally Posted by incagraphy View Post
    i had a brief look at what over-modulation is. Even though it seems to be a bit different from clipping, it sounds like it happens when the transmitted volume is too high. However, when I look at the waveforms of this noise in my videos, it's not necessarily too loud, they do not reach to 0dB; the distorted noise happens even when someone is speaking as well as when the person is between sentences.
    I'm not hearing any distortion or static between sentences on the samples you posted. Checking your waveforms are what caused me to go back and edit my initial reply. The recorded levels are fine, which means the overmodulation is happening before the signal reaches the recorder -- which generally points to the transmitter. Is -18 an option? Also make sure the impedance on the output of your receiver matches the impedance on the input of your recorder. Both should be line or mic.
    Last edited by smrpix; 4th Nov 2015 at 15:33.
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  5. I think what you say makes sense. Doesn't the Zoom H4n have it's own precautions to prevent clipping, which would mean I don't see the overmodulation in the waveforms that get lowered by Zoom?

    What can make it confusing is the fact that there have been much louder speaking people in the group who did not have these distortions in their recordings.
    If I find such examples, or the distortions between sentences, I will post again.

    For the time being, I am adjusting to -18 just like you suggested.
    Thanks for the help smrpix.
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  6. on the next video I am working at, I found a section where the distortion happens in between sentences too. It's attached. I am also attaching the recording from Zoom H4n, converted to aif using QuickTime (sorry if that's not the right format. I am quite new). I added that because, I realized in my importing to Final Cut Pro, there is an audio analysis and it fixes the audio levels.

    EDIT: it turns out .aif is an invalid file type for VideoHelp, so I saved the section as a .mov and attached it again.
    Image Attached Files
    Last edited by incagraphy; 6th Nov 2015 at 14:18.
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  7. Best guess, that sounds like something mechanical such as clothing rubbing against the mic or cable. RF interference is also a possibility, but I would rule out mechanical issues first.
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  8. I have the same model system myself, and the sounds that I'm hearing are most likely caused by an intermittent electrical fault in the mic cable. The lavalier mic cable is very thin, and prone to damage with use. You can troubleshoot this by using a good pair of headphones with the Zoom recorder or an audio mixer, and flexing all the various cables to see where it makes noise. If it's in the lav cord itself, a new one is your best option. You can also try some contact cleaner on all electrical connections.

    Remember that this model uses the shield of the mic cable as a diversity antenna! If you hear what sounds like a burst of RF noise, it's still probably a cable or connector.
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  9. Member
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    I use a couple of the Sennheisers at my church (I'm the sound guy), and a problem we have on occasion is that the screw connector between the mic and the transmitter body-pack works a little loose and causes intermittent noise. And the signal coming out is pretty hot; I think I've got both set at -18 in the gain control. That doesn't sound like what the problem is here (it wouldn't explain the noise when nobody's speaking), but yeah, that's probably where you should have it set.
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  10. Yep, that threaded fastener needs to be snugged up before each use. Regular cleaning and dressing with something like Caig DeoxIT will help keep contact noise down. I don't know of any manufactured burnishing tools for smaller phone jacks. A bit of pipe cleaner covered with DeoxIT or similar should work fairly well.
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