Technical numeracy

ADSR graph

What does a waveform graph show?

How displacement (or voltage) changes over time, between its maximum positive and maximum negative values and around a zero line.

Pic of waveform graph

What’s the purpose of a logarithmic scale?

Represents orders of magnitude as a linear change.

Examples of logarithmic scales in music tech

The decibel scale and frequency values on a filter or EQ graph

Logarithmic scale diagram

Why are EQs organised in this way?

Because we have a greater sensitivity to lower frequencies.

What is the decibel a unit of?

Sound pressure level (SPL)

Why do decibels use logarithmic scales?

Because our ears hear sound pressure logarithmically.

(Eg a chainsaw is many times louder than a conversation, but we don’t perceive it like that)

What are the three loudness measurements?

Peak

RMS

LUFS

What does peak volume measure?

The loudest moment in an audio signal.

When is peak volume useful?

Prevents clipping/distortion in a mix (or can also create pumping effects).

If the peak goes above 0dBFS, clipping occurs

What is RMS volume?

Root mean square - measures the average volume of the audio signal

What is RMS volume useful for?

Gauging the volume of a track during mastering

What happened in the loudness war (90s to 2000s)?

Producers increased RMS levels

This was done through heavy compression/limiting

What was the result of this?

Less dynamic range in songs

What is LUFS volume?

Loudness Units relative to Full Scale.

It measures perceived loudness of humans.

Where is LUFS volume used?

On streaming services (eg Spotify, Apple Music) - they use LUFS normalisation.

What is frequency of a wave?

The number of waveform cycles per second (Hz).

What’s the period of an oscillation?

The amount of time a single cycle takes.

How are frequency and period of an oscillation related?

Directly related:

Where frequency = f and period = T

f = 1/T

T = 1/f

FREQUENCY AND INTERVAL CALCULATIONS: How do you calculate a frequency an octave higher than the original frequency?

Double the value of the original frequency.

Eg an octave up from 1000Hz is 2000Hz

How do you calculate a frequency an octave lower than the original frequency?

Divide the value of the frequency by 2.

How do you calculate a frequency a perfect fifth higher than the original frequency?

Times the value of the original frequency by 1.5

Because this is the mid-point between the original frequency and the octave higher.

(Divide by 1.5 for perfect fifth below)

How do you convert a decimal to binary (8 bit)?

Fit the number into the 8 buckets:

128 64 32 16 8 4 2 1

Eg 150 in binary is 10010110

How do you convert from binary to decimal?

Total up the numbers with a one in their column.

Eg for 10010110 - 2+4+16+128 = 150