EQ and Compression Techniques For Vocals and Acoustic Guitar
Compression
When I first started reading about compressors I was hopelessly lost. The terminology was technical in an almost mean-spirited way and I couldn’t make heads or tails of what was being written. To keep things simple, I think of compression as a way of evening out the loud and soft parts of any vocal or instrument so that its behavior is a bit more predictable. In other words, compression brings up the really soft spots and tames the really loud spots so that you’re not constantly reaching for the volume fader on your mixing board (or virtual mixing board on your DAW). In its simplest form, a compressor, whether a hardware unit or a plug-in, will squeeze the Read more
Room Acoustics
Topic List
- Direct Sound
- Early Reflections
- Absorption of Early Reflections
- Later Reflections (Reverberant Sound)
- Reverberant Field
- Direct Sound to Reverberant Field
- Steady State Reverb Level
- Critical Distance
- Reverberation Time
- Room Size Issues
- Reverberation Time with Frequency
- Reverberant Time with Mixed Surfaces
- Reverberation Time Design
- Issues in Reverberation Design
- Room Modes and Standing Waves
- Critical Frequency
- Ideal Live Room Characteristics
- Ideal Control Room Characteristics
Standing Waves
A standing wave is a sound wave that is the product of continuously reflected back & forth sound wave between two parallel walls/surfaces whereby the incident wave and the reflected
wave are in phase.
Lowest Frequency (F) = 343 / 2 x L
The frequency of a standing wave within a room will be determined by the distance between the walls/surfaces and is a product of the interaction of the initial and reflected sound but distinct from them.
With a standing wave, the reflected wave is synchronized with the incoming wave as they pass by. There are mutual cancellations and reinforcements that do not move – hence the term ‘standing” wave.
Points of max amplitude = pressure anti-nodes
Points of min amplitude = pressure nodes
‘Standing waves are directly dependent, in conception, upon the physical phenomena of reflection. The wave front will hit the wall then reflecting back to the sound source. In effect, one wave traverses to the left whilst another to the right. The interaction between the two creates a stationary standing wave that is a product of, yet distinct from, the two waves that generate its existence.’ (Everest, p.240)
The creation of a standing wave occurs by the superposition (the placing of something on or above an existing thing – noun) of these two travelling wave.
‘The dimensions of a studio or listening room determine its characteristic frequencies much as though there were a north-south pipe, an east-west pipe, and a vertical pipe, the pipes corresponding to the length, width, and height of the room, respectively.’ (Everest, p.319)
- Standing waves are also most prominent for 400Hz signals and below due to the amount of energy that they carry in vibrating through the air.
- What do you notice most when outside a live music venue?
- Do you hear much high frequency energy escaping?
- Notice the vibration from bass in pubs and clubs whereas higher frequencies carry less energy and hence absorption or diffusion can occur through materials at a greater and more effective rate than for low frequencies.
The lowest resonant frequency (standing wave) between 2 walls will be equal to the following: › F = 344 / 2 x Distance (meters) › Example: 5 meters apart > @ 344 / 2 x 5 = 34.4 Hz Standing waves will also occur at whole number multiples of the primary resonant frequency › Example
- 34.4 Hz x 2 = 68.8 Hz
- 34.4 Hz x 3 = 103.2 Hz
- 34.4 Hz x 4 = 137.6 Hz
These resonances are called MODES
