TL;DR: Audio mixing is a nuanced process that involves four essential elements: compression, noise gates, deessers, and equalization. Compression ensures a consistent audio level by reducing loud sounds and amplifying softer ones. Noise gates help remove low-level signals and attenuate audio leakage, while deessers manage the issue of sibilance, a slurred “S” sound. Equalization adjusts the balance of frequency components in an audio signal, with techniques like subtractive equalization and frequency juggling proving useful for certain scenarios. Different instruments require specific EQ adjustments for optimal sound performance. Understanding and effectively applying these techniques can significantly enhance your audio mixing skills.
Introduction
Audio mixing is a delicate art that requires a fine balance of different processes. This article will explore four key audio elements: compression, noise gates, deessers, and equalization. These elements, when used accurately, can dramatically enhance the quality of your audio mix.
Compression
Compression is a vital tool for maintaining consistent audio levels, as it reduces the volume of loud sounds and amplifies the softer ones. When using compression, you aim to smooth out the sound and avoid significant changes in loudness. While it is critical, a little goes a long way; over-compression can lead to an unnatural, squashed sound. To achieve optimal results, experiment with different attack and release times, which control how quickly the compressor responds and releases. Remember, slower attack and release settings work well for preserving the punch and dynamic range.
Noise Gates/Expanders
Noise gates are tools used to remove low-level signals such as basic noise, coughs, and track leakage. Their primary purpose is not to remove leakage entirely but to attenuate it enough so that it’s barely audible. Noise gates are highly sensitive, so they require thorough experimentation. To use them effectively, you set the threshold to the middle to ensure you remove everything unwanted while preserving the rest of the audio. The range, which is usually set between -12dB to -18dB, controls how much the noise will be reduced. Digital systems also offer a look-ahead function, which analyzes the signal to ensure the gate only reacts to peaks.
Deesser
A deesser addresses the issue of sibilance, a slurred “S” sound that can occur due to improper micing and compression. With just two controls, frequency and range control, deessers are simple yet effective. The frequency allows you to set where sibilance is occurring, and the range determines the amount of gain reduction.
Equalization
Equalization is the process of adjusting the balance of frequency components in an audio signal. Equalizers can vary dramatically, so it’s best to experiment to find the one that suits your taste. A parametric equalizer is one common type, giving you control over the gain, frequency, and Q or quality of the filter. Avoid pushing equalizers too hard as they can easily cause distortion.
Subtractive Equalization is a technique used by top audio engineers to improve audio by attenuating frequencies instead of boosting. When EQ is boosted, phase shift is added, which can distort the sound. Subtractive equalization works best between 200 to 600Hz and 2kHZ to 4kHZ.
Another technique to enhance the sound is Frequency Juggling, which is used when instruments clash because they share fundamental frequencies. It involves alternating between two instruments, applying subtractive EQ to one and boosting the same frequencies in the other.
Equalization Principles and Instrument-specific EQing
When EQing instruments, each has its unique characteristics that need specific attention. From drums to guitars to vocals, every instrument has frequencies that require boosting or attenuation for optimal audio performance.
For instance, for a snare drum, adding crispness can be achieved by boosting at 5kHz, while a boost between 140Hz to 240Hz can enhance fatness. For an electric guitar, adding fullness may require a boost at 240Hz to 400Hz, while a boost at 4kHz can give guitar pick noise and brightness.
Vocals, particularly, require special attention. EQing can be used to either push vocals upfront or move them back in the mix. For male vocals, a boost at 125kHz to 250kHzcan offer more presence and chest resonance. For clarity, a boost between 2kHz and 5kHz can be effective, and to add ‘air’ to the vocal, a boost at around 10kHz can be employed, taking care to avoid adding sibilance to the recording.
Background Vocal EQ
The goal for background vocals is to avoid competition with the lead. A cut between 2kHz and 5kHz can prevent clashes with the lead vocal, and a boost at 6kHz can add brightness. A high-pass filter around 150kHz can help to clean up background vocals.
Piano EQ
Since a piano can play almost any role in an arrangement, it can be EQ’d in a variety of ways. A boost between 80Hz and 120Hz can add fullness to the piano, while a boost between 2kHz and 5kHz can add more presence.
Equalization of instruments involves some general principles that can be a handy guide:
- If the sound is muddy, cut around 250Hz.
- If it sounds honky, cut around 500Hz.
- Cut to add clarity, boost to make things sound different.
- Use a narrow Q when cutting (6 – 10) and a wide Q when boosting (0.5 – 2).
- To make something stick out, roll off the bottom, to blend in, roll off the top.
Lastly, remember to use the bypass feature often during these processes to ensure that your adjustments are improving the audio and not degrading it.
Conclusion
By understanding and applying these techniques – Compression, Noise Gates, Deessers, and Equalization, you can greatly improve your audio mixing skills. However, like any craft, it takes time, practice, and patience to perfect. Happy mixing!