[Audio problems] "weavy sound" at low audio level
 

Hi there,

I own a XM2 (PAL of GL2) and a VX2100. I do videos of fireworks displays only so I have a special question:

I do film with manual audio settings only. Normaly I adjust the left/right audio level to ~ half of maximum (3 o'clock position) - this works most times for the explosions of the fireworks and the music at musical displays.

When recording a fireworks display where I stand relative close (50-150m) to the music speakers and the music is played very loud I have to lower the audio levels to ~ 5 o'clock position which is very close to minimum.

Now I have the problem that in this ~ minimum position the recorded music is often somehow "weaving" in a sinus curve: it's permanently getting louder and more silent again.

I think that this has something to do with wind, because this happens very clearly when it's windy at the displays. Then I do use a Windex fur microphone protection over my Audio Technica 822 external stereo microphone.

My question: is this "weaving" sound at low audio levels a common problem?
I think that my VX2100 does not have this but I could not compare exactly yet. Where does it come from? From the wind (when hearing the music live at the display the sound is not that weaving)? From the Windex fur protection?

Any comments or hints are appreciated!
Many thanks in advance

Markus

Markus,

Sounds like AGC (Automatic Gain Control) is attempting to dynamically noramalize the sound levels. When the sound is softer, it gains up, and then when the sound is louder, it gains down. The delay or lag in making these changes might be what you are referring to as "Weaving".

Try turning off AGC if your cam provides a user selectable option to do so.

Hi Patrick,

thanks for your answer!

No, I am using manual audio control only - so no AGC. You are right - with AGC any explosions shuts down the microphone for a second immediatly and the music gets very silent.

My problem seems to be in relation with outdoor filming in windy (not stormy, but windy) situation. When recording the mentioned very loud music from outdoor speakers (at low level manual audio setting which is necessary, otherwise the music is totally overdriven) the wind takes away the sound somehow in "sinus curves": the music is slowly getting more silent/softer and louder again and again.

But - and this is my problem - the recorded audio is much more weaving then it was noticable when performed at the display. So something is dramaticaly increasing this weaving effect:

- the low level audio setting? It's not good to come close to the minimum setting of the audio levels at the XM2/GL2?

- the Windex fur protection of the microphone?

It's very difficult to reproduce these situations so I have to ask...

Thanks in advance,
Markus

Markus,

Don't have time to search for it and provide the link, but somewhere in the 'Now Hear This' forum here in this community is a thread discussing physically taping a microphone to the speaker (like with duct tape, or, since its film related, gaffer's tape). Might have some relevance and utility for your situation. Your mileage may vary.

Markus,

Found the thread:

http://www.dvinfo.net/conf/showthrea...taping+speaker

Dear Patrick,

thanks for finding the thread! No, it seems that they really do not have the problems I have - they even tape the microphones to speakers - so I have the problem with loud music even when I am ~ 100m away!

I checked my last tape of two displays at the some location from the same position with same audio level on my XM2 (5 o'clock position). One day was alomst without wind, one day had wind:

On both displays the sound is "destroyed" in the loud parts of the music or the parts with low frequencies (drums, disco beats). The sound is then very "scratchy/overdriven" - although the audio levels do not hit +12db.
That what I described with "getting louder and softer again and again" is not really the volume, but a permanent "cutting the higher frequencies" (e.g. voices) again and again - so without the higher frequencies the music sounds more silent/bad.

The wind increases this effect, but even without wind it is noticable. So, what can cause this "scratchy, overdriven, weaving" sound?

- my Audio Technica 822 microphone?
- the Windex fur protection?
- the low audio level setting on my XM2?

Back to my question: does anybody mention already, that low audio levels on the XM2 but very loud music to record produces this destroyed audio recording?

Many thanks
Markus

Markus,

Reading your latest post, I get the impression your mic is just providing an overly 'hot' signal to your cam.

You should study this thread http://www.dvinfo.net/conf/showthrea...5&pagenumber=1

I think it will lead you to the conclusion that you need to try the MIC ATT (microphone attenuate) switch on your XLR box, or if no XLR box, you might need a -10 to -15dB inline attenuator for your particular mic.

Maybe one of the real pros could step in here and make sure I'm not spending Markus' money unwisely. Jay M or Matt G appear to be VERY audio informed.

Hi Patrick,

thank you so much for that hint! Yes, in this thread they seem to discuss exactly my problem. And guess what, this morning I thought by myself "maybe this MIC ATT menue entry at the XM2 could be an idea"...

So, I will try. As I said it is hard to reproduce the situation without a fireworks display with so loud music - but I will try to play some really loud music with my stereo player - see, if I can reproduce the effect and avoid it afterwards with the MIC ATT switch.

I will inform you!
Thanks again for the good input!

Markus

That's it!

I just tried to video a fireworks display with louuuuuud music coming from big speakers in front of me. Although in very loud sequences the music/sound becomes "waving/scratching" again, with the "MIC ATT" enabled in the menue it is much much better then without.

So, here we are - thank you!
Markus