Signal Processing (time-based effects)

1. Signal Processing (time-based effects) Delay, Modulation and Reverb effects

2. Why do we process sound for recordings and live music performances? • Signal processing is used to mold and shape the sounds that are used in an audio recording. • All commercial recordings and professional live performances make extensive use of signal processing.

3. basic rules that relate to sound processing: • Effects are best employed when the user actually understands what the effect really does to the sound. • Don’t over process sounds unnecessarily (less is more) • Applying effects should not make up for poor microphone technique and equalization • Effects will not substantially improve a weak composition, arrangement or performance.

4. Effects processors can be hooked up in three different ways: • In-line: The signal is sent directly into the unit from an instrument and then right into a mixer or amplifier. • Effects loop: Connection to the send and return (effects or aux) bus on a mixer or amplifier. This method is used if we want to add the same effect to a variety of different channels or parts at the same time. Example: Reverb • Insert: Inserted into a channel strip of a mixer.

5. Typical signal path:

6. There are three main types of time based effects: • Delay • Modulation • Reverb

7. DELAY • A delay unit records a sound and then reproduces the sound a little later. • Delay gives the listener the impression that the sound is being made in a larger environment. This is referred to as delay time or delay length. Delay time is usually measured in milliseconds (ms). • There are 1000 milliseconds in a second. • In the early days of recording delay was created with tape loops. These days delay effects are created digitally.

8. The Three Basic types of delay: • Slap Back • Doubling • Repeated Delays

9. SLAPBACK • The simplest form of delay • Slapback is a single repeat of a sound (35 ms to 300 ms). • This effect is most commonly used to thicken a vocal or instrumental part.

10. DOUBLING • A doubling effect is created when delay time is set to less than 35ms. • This gives the impression that two people are performing a part in unison. • When doubling always use prime numbers for delay times (ex. 1, 3, 5, 7, 11, 13... etc). This yields better results when a recording is heard in mono.

11. REPEATING DELAYS • Repeating delays are achieved with the use of a regeneration control dial (feedback). • This dial feeds the delay signal back through the unit. • The higher the feedback the greater number of repeats.

12. Calculating Delay Repeats • Delay repeats should line up with the rhythmic groove of a song. • There is a simple formula to calculate the delay time that will repeat in quarter notes along with the tempo of a song. 60 000  bpm (beats per minute) = delay time per beat (quarter note) in milliseconds

13. Delay Time Table:

14. Modulation • The modulation control on a delay unit is used to create other popular effects such as chorus, flanging and phase shifting. • These effects involve pitch variations that are created with a LFO (Low Frequency Oscillator) that continually varies the delay time. • Altering the range of delay time (depth) and the speed of change (speed) will create a great variety of modulation effects.

15. Phase Shifting • Phase Shifting occurs when a delayed copy of a sound is heard directly after the original. • The two sounds are so close together that they almost cancel each other out. • This is known as phase cancellation. To achieve this effect the delay time is set from 0.2-2ms.

16. Flanging • Flanging is a metallic effect that was originally created by playing two reel to reel tape recordings of the same tune simultaneously. • The engineer varied the speed of one of the tapes by touching the edges of the reel (“the flange”). • This created a short delay that varied anywhere from 10-20ms between the sounds. It is best used on Rhodes pianos and guitars.

18. Chorus • Chorus attempts to simulate the time and pitch variation of a choir. • This works well on background vocals, guitars and keyboards. • The delay time is set anywhere between 15 and 35ms. • With the longer delay time we actually hear a noticeable pitch variation.

19. Enhancing modulation effects • All of these modulation effects can create even more interesting results when they are used in stereo. • Most modern effects devices are available in stereo. • Quite often they will even turn a mono signal into a stereo processed sound.

20. REVERBERATION • Reverberation is really just a series delays. • Reverb devices attempt to simulate the sound of a specific acoustic environment. • Basically every modern recording and most live performances make extensive use of reverb to help make the music sound larger than life to the listener.

21. Variables (dials) that can be altered on a reverb device to simulate an environment: • Pre-delay: time delay that happens before the reverb is heard. • Reflections: the number of times that a sound bounces around a room • Diffusion: amount of time between the reflections • Decay time: the amount of time it takes for a sound to decreases to one millionth of its original sound pressure level. • Density: the time spacing of the initial reflections.

23. Most Common Reverb Settings: • Hall: smoothest and richest • Chamber: echo chamber • Plate: bright • Room: bedrooms to large conference rooms • Reverse: backwards effect • Gated: lots of reverb that is closed off quickly (Phil Collins drums)