Contextualizing and mixing production conversation, especially during interviews, involves a precise balance of clear, direct voice and enough indirect, ambient background sound. When there is excessive background noise, speech may become difficult to understand.
Contextualizing and mixing production conversation, especially during interviews, involves a precise balance of clear, direct voice and enough indirect, ambient background sound. When there is excessive background noise, speech may become difficult to understand. Audio Cleanup Services understands that the speech-to-noise ratio indicates the proportion of background noise to speech. The increased speech-to-noise ratio is advantageous, but also for on-set communication channels.
There are a variety of techniques for raising the speech-to-noise ratio, each with its own set of benefits and drawbacks.
1. Reduce the distance between the subject and the mic, increasing the distance between the microphone and ambient noise.
Reducing the distance between the subject and the microphone is the most effective way to increase the speech-to-noise ratio. Consider a live performance in which the singer places the microphone right in front of/on the roof of their mouth.
Similarly, lavalier microphones are routinely used to capture production dialog in high-noise environments. Compared to boom-mounted microphones, lavaliers allow closer proximity to the lips, improving the speech-to-noise ratio.
2. Eliminate sources of ambient noise.
It is preferable to eliminate acoustic noise sources before recording. For example, turning off a neighboring air conditioner is far easier than attempting to remove the sound in post-production. Moving to a different place is also the ideal solution if there is a problem with traffic noise. Often, simply saying it is easier than actually doing it.
Additionally, it is critical to minimize wind noise. Wind noise can wreak havoc on mic preamplifiers, resulting in difficult-to-remove aberrations. When utilizing microphones outside, make sure you use fit windscreens.
A quick listen with headphones frequently reveals invisible acoustic sources such as wind noise.
3. Utilize directional microphones.
Off-axis audio signals are less susceptible to cardioid, super-cardioid, and polar shotgun patterns. This property can be used to reduce background noise. When it is impossible to eliminate noise sources, position microphones so that the noise sources are in the null, or least sensitive, region of the microphone’s polar pattern. The opposite design dictates the null angle. While a cardioid mic’s null angle is 180 degrees off-axis, the null angle changes as microphones get more directional. The null angle of a super-cardioid microphone is between 127 and 233 degrees.
4. Filter the microphone or the first amplification stage with a low-cut filter.
The bulk of ambient noise is pink-noise-like, with most energy concentrated at low frequencies and less at higher frequencies. Because there is minimal voice energy below 100 Hz, it is a good idea to use a high-pass, also known as a low-cut, filter during interviews. For applications where speech intelligibility is more critical than keeping a natural, full-sounding voice output, a substantially more aggressive high-pass filter of up to 320 Hz can be used. Remember that telephone-grade audio has a frequency response of 300 to 3,000 Hz, which covers approximately 90% of speech energy.
Numerous microphones incorporate high-pass filters. To begin, place the filter on the microphone. If you require further high-pass filtering, switch it on in the preamplifier. When both the microphone and preamplifier have high-pass filters, the slope of the filter increases, resulting in a more rapid falloff of low frequencies.
5. Reduce the number of unused microphones.
“Open” microphones are those that are currently recording. When the number of open mics is doubled, the overall background level in the mix increases by 3 dB.
Conclusion
There are numerous approaches for improving the comprehension of dialog recordings. Specific techniques take advantage of real-world modifications, such as changing the microphone’s location, shutting off sources of background noise, or deploying windscreens. Others make use of software plugins.