Of all the technical issues facing an instructor making an online lecture video, audio has to be near the top of the list. A video with noisy, distracting audio is hard to listen to for long periods of time, makes comprehension difficult for students whose language is not native to the audio track, and ruins the dialogue the instructor is trying to establish with the student.
Here are some tips towards getting great audio in your recordings:
- Use the right microphone — A microphone that’s up-front and close to the instructor, e.g. a lavalier or headset microphone, is probably the best way to capture decent audio. A shotgun microphone aimed at the speaker might be second best. Microphones that are in a laptop, part of a tablet, or that are sitting away from an instructor on a desk or mounted overhead will not pick up voice as cleanly and will be prone to adding laptop noise, room noise and other impairments. Microphones that are built into the video camera you may be using are not the best sources of good audio.
- Use a professional pre-amp to boost the microphone-level signal to a line-level signal for transmission to the recording equipment. Something similar to a Mackie 402-VLZ3 Compact Audio Mixer is an example, and well worth the cost. Microphone-level signals are subject noise pickup and are not suitable for transmission over long distances. Use balanced audio cables (XLR connectors) wherever possible. These cables help in canceling electromagnetic noise interference. USB microphones are great in that they convert weak microphone signals to digital signals that are immune to noise. Our lecture-camera recorder only accepts USB audio.
- Wireless microphones, if not good quality, will add unwanted hiss into your recordings. Use a wired microphone if possible.
- Review and consider the acoustics of the room where the recording will be done. Are the walls bare and prone to echo sounds? Professional recording studios have special foam on the walls to capture all reflected sound. Perhaps you can find, instead, a room with curtains or books lining the walls. What about fans, air-conditioners, HVAC or other unwanted sound sources? These don’t add any value to your recording. And finally, close out other distracting noises like hallway conversations, cellphone ringers, barking dogs and kids screaming in the background.
- Use a high sampling rate for your audio – 44 or 48 KHz. minimum.
- Record to an uncompressed format for your original (i.e. AIF or WAV format). Formats like MP3 are already compressed and if they need to be decompressed and recompressed as part of your video editing process you will create a second-generation audio recording and will lose quality.
- Finally, when creating your published online video, don’t shortchange the bit-rate settings for the audio. Settings like 11 KHz or 22 KHz will make you sound like an overseas telephone operator. Not a good idea.
Some consideration of the points above will not only make your audio good, but really great.