Internet Sound Institute - How to Improve Sound for Video

How to Improve Sound for Video

Remember the 16 mm film projector with the "built-in" loudspeakers? The sound was distorted with little high frequency response or intelligibility. It was loud for those sitting close, yet couldn't be heard by those sitting further away.

Well, you don't have to live with poor sound for your video anymore. The simple tips in this article will help you achieve better sound for your video. While this article focuses on VCR and camcorder applications, the principles can be applied to new technology as well.

Direct Box Improves Audio

The direct box (as in Figure 1) is designed to accept an audio signal from a VCR, DVD, CD/cassette deck, mixer, keyboard or string instrument with a pickup. This box converts the line level signal to a microphone level. Using a regular microphone cable, connect the output of the direct box to a nearby microphone jack. The audio from the video can now be heard in the main sound system or even a portable sound system.

Figure 1
A direct box converts the signal level to a microphone level.

Direct boxes vary in cost and features. For the most flexibility, select a model that has several types of input connectors.

VCR Audio Feed

The sound track on a VCR or DVD can be fed with a direct box to the main loudspeaker system. Look for the audio output(s) on the VCR. Make certain you are plugging into an audio output, not a video output (it probably won't hurt the system, but you will hear strange sounds). The stereo audio outputs, normally RCA phono jacks, are usually color-coded white and red.

If it's important to hear both channels from a stereo video, you may need two direct boxes. It's better to use one on each channel rather than a Y cable.

Audio for Video Recording

The recording process is another area of sound for video. Camcorders have become an integral part of productions for both adults and children. Although most camcorders have an attached microphone, it is difficult to achieve quality sound with these microphones. The attached microphone picks up a lot of noise from the audience. And even if the audience noise isn't a problem, the camcorder is usually far away from the audio source. The result is very hollow sound.

Three Ways to Improve the Sound for Video

Three techniques to improve the audio for your video recordings are highlighted below:

1. Place a microphone close to the source of sound (Figure 2). This will help reduce the reverberation effects and crowd noise. However, a cable will have to be run so you are physically locked to one camera position. Also, since there is only one microphone, you will not have much control on the audio balance or mix. Careful positioning of the microphone will minimize this problem.

Figure 2
Use an extended microphone to achieve better sound quality.

2. Feed the signal from the sound system mixer into the microphone input jack on the camcorder. There are two ways to do this. If your school has a fairly current Hearing Assistance System (Figure 3), plug a cable from the earphone output jack on the pocket receiver into the microphone input on the camcorder. Be sure to test and adjust the receiver's volume control to prevent distortion on your recording. You will likely need an attenuation cable to decrease the volume to the camcorder. Also, make certain the batteries in the personal receiver are fresh. This approach allows the camcorder operator the freedom to go anywhere in the room.

Figure 3
Use a personal receiver to feed the camcorder.

3. Use either an existing microphone line or an external cable to feed sound to the camcorder. The output of the mixer is plugged into a direct box. The microphone level output from the direct box is then plugged into a microphone extension cable. On the other side, you will need an adapter cable with a female XLR microphone connector and a mini phone connector (like the one in Figure 4). Again, be sure to check the recorded audio to make sure the input level is ok. A signal that is too high will cause distortion. A signal that is too low will be noisy. Adjust the mixer output to get the right level.

Figure 4
Use an adapter cable to connect your camcorder to the direct box.

Sound Planning Tips

Professional-sounding audio for your video tape requires effort and planning. You may want to consider placing a microphone in the following areas for the video recording.

1. Solo voices or small groups will probably need a microphone.

2. If you want to hear the audience response, add a microphone for the audience and direct that to the video recording. This record mix should be separate from the main mix because you cannot add audience sound into the main sound system without feedback.

by Travis Ludwig © 1996 Internet Sound Institute (www.soundinstitute.com). This article is for personal use only. Any commercial reproduction is not permitted without permission. To obtain permission, contact ISI at hopi@soundinstitute.com

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