Sound Training 2B

Sound Training 2B

23/30th November 2011

JP & JC

Objectives

• Understand some theory about sound and the equipment used

• Learn how to fully build and plug in a sound rig for a typical band night in Rubix

• Learn how to soundcheck and mix a drum kit (and maybe other instruments)

Sound Theory

Sound in Air & the Ear

Sound is a type of wave, which our ears detect and convert into electrical signals

Wave/Sound Properties

• Amplitude• Frequency (1/Time Period)• Wavelength

The dB (decibel)

• “The decibel (dB) is a logarithmic unit that indicates the ratio of a physical quantity (usually power or intensity) relative to a specified or implied reference level.”

• dBu• dBF• dB(SPL)

Loudness (According to the Ear)

dBA “weighting” SPL follows the 40 phon curve

dBB “weighting” SPL follows the 70 phon curve

dBC “weighting” SPL follows the 100 phon curve

Common dB(A) levels

• 20 – rustling leaves

• 40 – bird singing / quiet talking

• 70 – toilet flushing

• 90 – heavy city traffic

• 110 – rock band

• 130 – pneumatic drill

• 150 – jet plane close by

The Law (at work)

• 80 dBA Leq over 8h (or 135dBC instantaneous) - ear protection available on request

• 85 dBA Leq over 8h (or 137dBC instantaneous) - ear protection issued

• 87 dBA Leq over 8h (or 140dBC instantaneous) - max legal level (after reduction by protectors)

Exposure & Recovery

Signal Sources, Speakers

& the bits in between

Microphone Types

• Dynamic (we use live)

• Condenser (we use live)

• Ribbon

• Piezoelectric

Dynamic Mics

• High SPL sources (e.g. vocals, drums, guitar)

• No power required

• Rugged design

Condenser Mics

• Low SPL sources

• Can be good for HF sounds e.g. cymbals, flute

• Require power (phantom power)

Mic Pickup Patterns

Typically used on stage

Other Sources

• Some instruments already output an electrical signal (e.g. keyboard, bass guitar, laptop)

• If unbalanced source (to be explained later) then usually plugged in via a DI (direct injection) box

Speakers

• Many sizes

• Certain sizes reproduce sound more efficiently than others

• Therefore, often many speaker sizes in one box

Active / Passive

In active systems, a crossover is used to split up the sound into frequency ranges to send to

different amplifiers and speakers

Active / Passive

Passive systems amplify the sound before splitting the signal to go to different speakers – only one

amp required

You may notice the wedges (aka monitors) have an active/passive switch – we usually use them in

active mode

Active / Passive

WARNING!!! Double definition!

Active/Passive can also refer to whether a piece of equipment has amplifiers built in.

E.g. RCF drum fills are a type of ‘active’ system

FOH & Monitor Speakers

• FOH speakers are used so audience can hear the act (usually just left and right speakers)

• Monitors are so the act can hear themselves play clearly (many sets of speakers – maybe 1 per band member)

Point Source Speakers

• Many speakers are pointed as to cover the listening area

• E.g. our Turbosound rig

Line Array Speakers

• Lots of small speakers joined together to work as one big speaker

• E.g. our d&b rig

Feedback

• Certain frequencies of sound get stuck in a loop between the microphone and the speaker

• The level of that frequency increases and causes the often painful ‘squeeling’ noises

Signal Path

Sound Cabling

• Balanced / Unbalanced

• Connector types

Signal Processing

Frequency Control

• “Equalisation” or “EQ”

• 2 main types• Parametric• Graphic

Filters

• Low Pass (LPF)

• Band

• High Pass (HPF)

Amplitude Control – Compressors / Limiters

“Reduce

dynamic range”

“Gets rid of peaks in volume”

Amplitude Control - Gates

Let sound ‘through’ when above a set level

Effects – Delay

Effects – Reverb

Phase

Now the fun bit…