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Old March 18th, 2006, 06:36 PM   #1
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Avoiding Room reverb

I have recently done a couple of interviews. One with a lavier radio mic and one with a beyer dynamic shotgun. In the lavier mic setup, a fair amount of background noise was picked up, including traffic outside the building. In the shotgun setup (in a small room, but mic about 12 inches from subject), there was about 2/3rds wanted sound and 1/3 reverb.

Are there techniques to reducing noise / reverb pickup in these situations, such as lowering gain or mic position etc? or does it depend on the microphone. When I hear sound from TV broadcasts it's usually, not only clear, but has a full tonal quality and very little noise.

Mic gain on the XL2 was set to manual in both situations, and the radio mic was set at -10db (sennheiser setup).
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Old March 18th, 2006, 07:32 PM   #2
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Declan,
There are some techniques you can use to minimize extraneous noise but assuming the mic is working properly you have to change the character of the sound reaching the mic to make a big difference. Mic placement is one of the easiest. Sometimes moving the mic a few inches closer to the subject can make all the difference in the world. Also some mics don't do well in some situations. There is a reason TV reporters use handmics.
Some rooms have a lot of reverb and the mics will pick that up. If you can't use sound blankets or other material to deaden the room the mic will pick it up. Try and hear what voices sound like to your ears in the room. If it sounds strange to you then it will likely be poor for the mic. Maybe you can change rooms.
The radio mic transmitter might have a sensitivity setting which might change how much background sound it picks up. If it is set up too high it will pick up the background. If it is set too low the mic won't have enough output.
Also different mic heads have different qualities so you might get better results in noisy situations with a different mic head. If you know what pattern the mic you are using has you can see if there are different mics you might want to try out. For example I use Tram Lavalier mics a lot and they have an omnidirectional pattern. If the subject I am recording is on stage with a PA then I might want a different more directional lavalier like the Sony ECM series to help avoid feedback and get more presence.Of course if the person turns their head away from the mic you might not hear them since the pattern is not as wide as the omnidirectional Tram. Placement can be key
The more you record sound in the field the more experience you will get dealing with difficult situations and you might realize that you need to use a different miking technique to get the sound you want or you live with less than optimal sound because you can't use that technique in the project for a variety of reasons.
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Old March 18th, 2006, 10:38 PM   #3
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The right mic for a given situation is better than the wrong mic, and good mics are better than cheap mics, but there is no subsitute for a good acoustical space and closeness to the subject. TV and movie studios have all of the above.
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Old March 19th, 2006, 07:08 AM   #4
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Quote:
Originally Posted by Declan Smith
I have recently done a couple of interviews. One with a lavier radio mic and one with a beyer dynamic shotgun. In the lavier mic setup, a fair amount of background noise was picked up, including traffic outside the building. In the shotgun setup (in a small room, but mic about 12 inches from subject), there was about 2/3rds wanted sound and 1/3 reverb.

Are there techniques to reducing noise / reverb pickup in these situations, such as lowering gain or mic position etc? or does it depend on the microphone. When I hear sound from TV broadcasts it's usually, not only clear, but has a full tonal quality and very little noise.

Mic gain on the XL2 was set to manual in both situations, and the radio mic was set at -10db (sennheiser setup).
Shotguns often give problems in reflective environments as their directivity is highly dependent on frequency. As a result shotguns only selectively ignore reflections. Those that remain aren't so much supressed as they are given an objectional colouration. For that reason a hypercardioid is often preferred over a shotgun indoors. While its front lobe is a bit wider than on a shotgun, its supression of off-axis response to the rear where a lot of reflections are coming from is much better and not as frequency dependent, helping avoid that "subject hollering in a well" sound of reverb with added bass emphasis.

For the lav, a cardioid is often less prone to noise pickup than is an omni, with the trade off that the talent can't be as free in their head movement. Since people generally look in the direction of the camera or the interviewer in an interview setting it may not be a problem but it can become one in dramatic films where there's a lot of subject movement.

Hope this helps ...
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Old March 19th, 2006, 01:33 PM   #5
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Quote:
Originally Posted by Steve House
Shotguns often give problems in reflective environments as their directivity is highly dependent on frequency. As a result shotguns only selectively ignore reflections. Those that remain aren't so much supressed as they are given an objectional colouration. For that reason a hypercardioid is often preferred over a shotgun indoors. While its front lobe is a bit wider than on a shotgun, its supression of off-axis response to the rear where a lot of reflections are coming from is much better and not as frequency dependent, helping avoid that "subject hollering in a well" sound of reverb with added bass emphasis.

For the lav, a cardioid is often less prone to noise pickup than is an omni, with the trade off that the talent can't be as free in their head movement. Since people generally look in the direction of the camera or the interviewer in an interview setting it may not be a problem but it can become one in dramatic films where there's a lot of subject movement.

Hope this helps ...
Not having much experience at audio for video, I'm confused on one point. I thought that supercardiod or hypercardiod were shotgun mics. But if I read this right, it sounds like they're different. Are there differences other than the ones that you mentioned?

And which category would the AT897 fit in?

If you were going to be interviewing small groups of people indoors and/or outdoors, and were going to get a Sennheiser Evolution G2 wireless lavalier along with plug transmitter, would the AT897 or the Electro Voice RE50/B omni be a better choice to go with that? Or is there a hypercardioid you recommend? Or would you recommend another setup entirely? Cost is definitely an issue.

Dale
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Old March 19th, 2006, 02:35 PM   #6
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Strictly speaking a mic is called a shotgun mic because of its shape rather than its pickup pattern per se. Most shotguns are line+gradient pickups with a supercardioid polar pattern but there are other mics that can also have a super- or hypercardioid shaped pattern. One characteristic of a line+gradient mic is they tend to lose their directivity at the lower end of the frequency spectrum, in some cases the pattern almost becoming omnidirectional at the lower frequencies. The 897 shows a fairly typical shotgun pattern with definite rear and side lobes at lower frequencies.

The AT897 and the EV RE50 are very different. BTW, you do realize with the G2 you'll be able to use either the lav and bodypack transmitter or the buttplug transmitter and another mic, but not both at once? Will you have an interviewer in the shot holding the mic and pointing it at the person responding or do you plan to put the mic on a boom or on the camera? The 897 could be hand-held by a practiced interviewer but handling noise could likely be a signifigant problem. The RE50 is designed to be hand-held and wouldn't work from the camera position and probably not very well from a boom either. But frankly, the RE50 is inexpensive enough to put both of them in your kit to give you maximum flexibility.
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Old March 19th, 2006, 02:43 PM   #7
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Quote:
Originally Posted by Dale Lundy
Not having much experience at audio for video, I'm confused on one point. I thought that supercardiod or hypercardiod were shotgun mics. But if I read this right, it sounds like they're different. Are there differences other than the ones that you mentioned?

And which category would the AT897 fit in?

If you were going to be interviewing small groups of people indoors and/or outdoors, and were going to get a Sennheiser Evolution G2 wireless lavalier along with plug transmitter, would the AT897 or the Electro Voice RE50/B omni be a better choice to go with that? Or is there a hypercardioid you recommend? Or would you recommend another setup entirely? Cost is definitely an issue.

Dale
The above two mics are exactly what I have (plus the beyer dynamic shotgun). I have "got by" with these in most situations, but now I want to improve the results I am getting and learn how to obtain good sound in varying situations. In the lavier setup, I had very little control in terms of the room or ambient sound, so perhaps mic placement / gain settings could have been tweeked.

As for the shotgun setup, it was 14 inches from the speaker pointing up towards the mouth. There was a wall behind him but not im front. The room does have a little reverb (heard naturally) but it seemed more emphasized when recorded.

There have been some great comments. It would be useful to understand whether these mics are up to the job, or rather, recommendations as to when they should / should not be used, and also suggestions of other mics that would be useful (bearing in mind budget!).

I agree about practice, practice, practice. After all, sound recording is a profession in it's own right.
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Old March 19th, 2006, 03:53 PM   #8
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Steve, thanks for your explanation. It's helpful. Yes, I had figured out that it was either/or between the lav mic and a mic plugged into the buttplug transmitter. That's part of my dilemma. There will be some cases where I'll be recording a single individual and the lav I expect would be a good way to go. In other cases I may want to record 2 or 3 people in a small group and 2 or 3 lavs is not practical for me right now. It sounds like if there is an interviewer who knows how to position the mic, an RE50 would work. If not, it sounds like an AT897 or some hypercardioid on camera or a boom might be an second-best alternative to several lavs? Am I understanding that right?

Declan, you said the lav setup did not work out well because of lack of control over ambient sounds. Were the results acceptable, just not great, or were they poor?

Does someone know what kind of range the RE50 or AT897 has?

Dale
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Old March 19th, 2006, 04:41 PM   #9
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Dale

The results were acceptable, by far the prodominent sound is that of the interviewee, however, there was changing background noise, particularly a high pitched whistle coming from a road sweeper. I am cutting the audio about (with overlayed pictures on the interview) and in some places we have the roadsweeper, and others not, so putting a wildtrack over the top just seems to add more noise, and it's been a trial trying to get the audio to sound smooth. I guess the real peril here, thinking about it, was not having someone wearing cans during the interview. I was on my own, set the levels, then carried out the interview face to face with the camera running, and although I heard the sweeper, I thought it was too distant to be picked up, and most of the time was concentrating on what the interviewee was saying.

Lessons learned!!

Another difficulty I had was that the interviewee was nervous and thus wasn't speaking loudly, so the gain was set at -20db on the wireless mic.

Some good info about the different pickup patterns. Is there a particular mic (for low budget) that could be recommended for indoor, small room situations ?
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Old March 20th, 2006, 05:41 AM   #10
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Quote:
Originally Posted by Dale Lundy
...

Does someone know what kind of range the RE50 or AT897 has?

Dale
"Range," more commonly referred to as a microphone's "reach," is a misleading term because it's so relative. "Close micing" an F16 on a carrier deck would put the mic too far away to even hear normal speech. Optimal for any mic recording dialog is going to be something like 18 inches or less to maybe 2 feet from the speaker under exceptional circumstances. That's why I said the RE50 would not work on-camera - it'll get sounds, sure, but it's intended to be hand-held by the talent and that means it needs to be 6 to 8 inches from the speaker's mouth. There is no such thing as a long-range conventional mic that magnifys sound in the same way a telephoto lens magnfys an image - not even shotguns do that. Shotguns and hypers may give acceptable sound at longer distances in some circumstances because their rejection of sounds coming from other than where they're aimed let's you increase the gain more before background sounds get too intrusive. But the inverse square law applies to sound as well as it does to lighting - when you double the distance the mic is from the source, the level of the desired sound relative to any background noise, room reverb, etc, falls off by a factor of 4 and beyond 3 feet or so quality sound becomes problematic with any mic.

On-camera mics are good for recording general ambient sounds, scratch tracks to guide sync for double-system sound or to guide later ADR in studio, and for run-and-gun ENG situations where sound quality takes a second place to the need to get whatever you can manage. But only very rarely would they be an acceptable choice for dramatic dialog or interviews, etc. At the distance your camera usually will be from the subject, even the most expensive mics simply won't work well.
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Old March 20th, 2006, 05:43 AM   #11
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Quote:
Originally Posted by Declan Smith
Dale

The results were acceptable, by far the prodominent sound is that of the interviewee, however, there was changing background noise, particularly a high pitched whistle coming from a road sweeper. I am cutting the audio about (with overlayed pictures on the interview) and in some places we have the roadsweeper, and others not, ...

?
Sounds like it's time for Sound Soap or similar noise recduction software.
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