Background Hiss

[Alan Van Vliet]

I am producing short (8 - 12 second) tennis instructional videos for web delivery. I am shooting with an XL1s, currently with an on camera mic.

I do my initial editing in Premiere and then export to QT Pro for encoding via H264 with the following settings.

48000 Hz
16 bit stereo
uncompressed
1/2 second interleave
upper field first

I have experimented with audio various settings but always seem to have background "hiss" or noise.

Any suggestions. I do need stereo sound and excellent quality as the sound of contact is the focal point.

Thanks, AL

[Garrison Hayes]

Originally Posted by Alan Van Vliet

I am producing short (8 - 12 second) tennis instructional videos for web delivery. I am shooting with an XL1s, currently with an on camera mic.

I do my initial editing in Premiere and then export to QT Pro for encoding via H264 with the following settings.

48000 Hz
16 bit stereo
uncompressed
1/2 second interleave
upper field first

I have experimented with audio various settings but always seem to have background "hiss" or noise.

Any suggestions. I do need stereo sound and excellent quality as the sound of contact is the focal point.

Thanks, AL

Hey Alan,

Try using Mono sound ( just 1 sided sound.) then doubling the audio tracks in post.

Another suggestion is to buy a Windscreen for your on board mic....that should help tremendously if all else fails.

[Waldemar Winkler]

The hiss is there because you recorded it. So, you begin a process of elimination to identify the failure points.

Where did it come from? That is important. Eliminate the obvious issues first. These are physical mic connections. This may sound silly, but check to insure you have the mic connection firmly in place. A mic plug the did not go in all the way invites all sorts of problems. Each microphone you use has two connection points. Examine all physical connections. Each one is a potential failure point. Eliminate them as reasons for odd audio.

Having done that, the issue becomes the real sounds present when you recorded the event. My guess is that you had the camera audio gain controls set to high. That is the best way I know to introduce unwanted audio. But, as mentioned in an earlier post, a good windscreen is essential. Lightwave makes a really good one. You could make your own (I've done that), but the home made jobs can't match the engineered ones.

I'm also guessing you are recording vocal commentary with an on camera mic of a subject speaking from a distance of 10 to 15 feet or more away from your camera. The only way to get top quality audio is to have the microphone as close to the source of the sound as possible. Three to four feet is all the best an camera mic can hope to get. Investigate other ways to get good audio. A good wireless system is a starting point.

[Alan Van Vliet]

Good thoughts, thanks.

I double checked my connections today (on camera mic) and all appears okay. I've always left the gain controls alone, unless I have inadvertently changed a setting, or possibly a setting in Premiere could be affecting things.

Most of my recording is more of live action (non-vocal) from a distance of about 30 - 40 feet, and for the most part on days with little or no apparent wind.

I am planning on getting a windsock. I'll check out the Lightwave.

I presume one other possibility comes from somewhere in the editing process, from the connections with the decks, computer, etc. I am checking that out as well.

I will follow up with any solutions.

AL

[Don Palomaki]

Hiss is often associated with using automatic gain setting, or having the talent too far from the mic so the gain is turned up and amplifying the basic noise level of the mic. With AGC, when there is little, no, or low level sound from the talent or scene, the camcorder gain increases amplifying any hiss from the mic along with the desired sound.

All mics and recording system have a noise floor - a basic noise level that is always there. Think back on the hiss associated with cassette recordings. (Higher quality mics and recoding systems usually have lower noise floors, and dynamic mics normally have lower noise levels than condenser mics).) As noted above, the trick is to get the mic close enough to the talent so that the desired sound is much louder than the noise floor of the mic.

An alternate method is to record the sounds separate from the video, and then dub them in as sound effects during editing.

[Alan Van Vliet]

Thanks Don,

If I understand correctly, the AGC compensates for the general lack of noise and essentially turns up the volume, creating the hiss. Can the gain control be run manually? If so, I assume it can be monitored through the headphone jack.

Due to the nature of tennis, 30 - 40 feet is the closest I can get, even in a controlled situation.

What I am most interested in capturing is the sound of contact, which is fairly loud (and very brief, as in 3- 4 milliseconds) in contrast with the other sounds of the bounce, footwork, grunting, etc.

Separate recording is not really feasible, as each individual shot has its own sound, and we are really teaching students to differentiate those sounds and play each shot accordingly.

I realize on camera mics are not really ideal, but the sound of contact is suprisingly quite good, it is the other noises that are distracting.

[Alan Van Vliet]

Is there any way to reduce the hiss in post production? As far as I know, the settings I am using in Premiere are okay.

48000 Hz
16 bit stereo
uncompressed
1/2 second interleave
upper field first

Are there any filters that can be used or various settings during encoding that would help. These are the settings I am currently using to encode through QT Pro.

AAC
Stereo
44 Hz
Constant Bit rate
128 kbps

Thanks, Al

[Alan Van Vliet]

I assume if I set the record level on the XL1s to manual, I can cancel out the AGC and set the audio recording to the desired level for the sound of contact.

Would the use of the Attenuator setting help to reduce this background hiss as well?

I have ordered a windscreen (not a windsock, thanks for the suggestion) and am looking forward to testing.

I checked a tape that was recorded a year ago, and it was much quieter in general. It was recorded on courts that are more buffered from the wind.

I will follow up with results.

Al

[Don Palomaki]

Sounds like you have found the manual aufdio settings. Going to manual tyrns off he AGC. Then you do have to keep an eye on sound levels.

An attenuator reduces the level of ALL sound, not likely to help, more likely to make things worse.

You can do some things in post production to reduce hiss, especially his between sounds of interest. They amount to audio filtering and editing. Some audio editing programs such as Adobe Audition include hiss (noise) fillters and other effects that can be use to adjust/correct sound. These capabilities can help significantly if judiciously applied.

Sounds like the contact you are interested in is the serve. Consider a good shotgun mic at the end of a cable. Put the camcorder where you need it and run cable to the mic a few feet from the server. Probably need an XLR converter too.

[Alan Van Vliet]

Thanks for your thoughts, Don.

As there is a great deal of down time in between shots, I used the rubber bands in Premiere to reduce the volume in between shots, and to accentuate the volume on the spike. Worked out pretty well. The hiss is covered by the sound of contact.

I've been reading up on the shotgun mikes, need to research a bit more. I plan to take a look at Audition as well.

Regards, AL

[Ben Lynn]

I'm a little late in posting this, but record a clean racket strike and use it in the video? Get your mic very close to someone with a racket and ball, have them hit the ball with the racket so you can record one good hit, then just cut and paste that one good sound every time there's a hit on the video. Even if it sounds fake it would be better than the hiss if the hiss is noticable.

Ben

[Waldemar Winkler]

Originally Posted by Alan Van Vliet

Thanks Don,

If I understand correctly, the AGC compensates for the general lack of noise and essentially turns up the volume, creating the hiss. Can the gain control be run manually? If so, I assume it can be monitored through the headphone jack.

Due to the nature of tennis, 30 - 40 feet is the closest I can get, even in a controlled situation.

What I am most interested in capturing is the sound of contact, which is fairly loud (and very brief, as in 3- 4 milliseconds) in contrast with the other sounds of the bounce, footwork, grunting, etc.

Separate recording is not really feasible, as each individual shot has its own sound, and we are really teaching students to differentiate those sounds and play each shot accordingly.

I realize on camera mics are not really ideal, but the sound of contact is suprisingly quite good, it is the other noises that are distracting.

AGC basically functions by turning gain all the up and then waiting for a sound to be picked up by the microphone. Once a sound is "heard" gain drops to the best balance the onboard audio system can manage, which is often not very good. As already indicated, the closer the mic is to the source of the sound, the better the quality of the sound.

Referring to your point of contact issue, may I suggest the following:
1. Pre record a top quality point of contact and insert it in post. This may not work for the teaching environment.
2. Put a wireless omni-directional lapel mic on the athlete. You should get some acceptable point of contact sounds as well as a lot of grunts and groans associated with the explosions of athletic energy. These can be edited out in post.
3. Investigate the parabolic microphones often used by nature videographers. Using a paraolic dish to focus distant sounds on a microphone quality audio can be recorded from impressive distances.

[Tony Nguyen]

Could it be the sound of your camera running? I get that problem where you can actually hear the motor of the camera running. It's faint, but I'm a little picky. Anyone know a solution to this?

[Waldemar Winkler]

Originally Posted by Tony Nguyen

Could it be the sound of your camera running? I get that problem where you can actually hear the motor of the camera running. It's faint, but I'm a little picky. Anyone know a solution to this?

Whether the lens motor noise, which I do not believe is the "hiss" originally referred to in this thread, is due to the close proximity of the microphone to the lens body or is being fed to the body of the mic through the chassis of the camera (vibration) is probably a topic for spirited discussion. I tend to favor the latter reason. In any case there are rubber shockmount accessories made specifically for the Canon XL cameras which significantly reduce motor noise. I have one on one of my XL1s cameras, which also has a furry windsock, and I hear no motor noise. I think it is made by LightWave. The other XL1s mic is stock, and motor noise is very noticible.