Recording sound: people, environment and equipment Tom Castle David Nathan Rob Kennedy

Outline 1.Situations 2.Psychoacoustics and sound stage 3.Microphones 4.Recorders 5.Methods and principles 6.Audio signals 7.Today’s practical 8.Defining digital audio 9.Compression 10.Carriers 11.Digitisation 12.Editing and converting 13.Principles

1. Situations

Situations (External) environment  access  electricity  external noise sources

... Environment (ext)  external noise sources (cont’d) examplepossibilities for dealing with it traffic  investigate, record in quiet time  face away  use damping materials  see also General principles kids  get them involved  show something to satisfy curiosity animals  choose time of day  see also General principles weather (thunder, rain etc)  try to minimise problems

Environment (close-up) Internal environment  Machines examplepossibilities for dealing with it Refrigerator  Survey what comes on intermittently  Turn off  Avoid! Motors, switching  Avoid electrical interference Fans  Unexpected noise introduced

... Environment (close-up)  Yourself! overlap, shuffling papers, mic handling, table thumping  Other people  Mobile phones (calling and polling)  Room acoustics (and what to do about it)  reflection vs absorption  isolation

2. Psychoacoustics and sound stage

Psychoacoustics  The microphone is not like the lens!  And doesn't have a brain attached!  Will pick up in all directions  Can't distinguish wanted and unwanted  Vision for your ears  Your brain recognises and rejects sounds  Recording process removes many cues  Therefore need to optimise recording process at point of capturing sound waves

“Sound stage”  Listening as a “hallucination”  Purpose of audio - for a human listener, who has:  ears  brain  spatial location  Our normal approach to recording is unscientific; reduces events to data  What is “fidelity”?

“Sound stage”  Spatial information is an essential part of audio  We are amazingly attuned to it  We should record in stereo ... or even ORTF (binaural)  listen to an example

3. Microphones

Microphones  Even more critical in the digital era  quality increase  mics are analogue  Types  dynamic vs condenser  mono, stereo, binaural  directionality OMNI

... Microphones CARDIOID

... Microphones DIRECTIONAL/ SHOTGUN/ HYPERCARDIOID

ORTF 17cm 110°

... Microphones  Quality  Placement  locating  mounting and handling

... Microphones  Connections and cables  plugs  types of cables  wiring for multiple, stereo/mono  Prices  Power sources  see

Microphone usage principles  Monitor what you will record and what you are recording and what you recorded  The Inverse square law is your friend

4. Recorders

Recorders  Recorders in context  Types and their strengths/weaknesses/implications  Quality parameters  accuracy (freq response, distortion, s/n ratio)  reliability  features  versatility  battery life and power sources

... Recorders  Connections  Media types, costs, properties, implications  Formats (see later)

5. Methods and principles

Methods  Quick guide to settings – levels, formats, AGC  A second recorder?  Using assistance  Monitor  Rehearsal  Playback to participants  Copying and backup  Handling and re-using media

General principles  Consistency principle  juxtapositions  optimise use of equipment  efficient processing  Microphone choice  Monitoring  Familiarity and skills with equipment  Power and batteries  A range of equipment, not the “perfect item”!

6. Audio signals

Audio properties  First analogue ... then digital

Signal parameters  Pitch kHz - human voice  fundamental 100 (m) – 200 (f) Hz  formants 800 Hz – 4+ kHz  harmonics, other, up to 15 kHz  Amplitude (power) dB  a relative and logarithmic measure  0 dB is reference point; sound of mosquito flying at 3m  max human is about 140 dB (pain at 120)  each 6 dB step perceived as doubling/halving volume

... Signal parameters  Signal to noise  ratio of wanted to unwanted sound data  the bigger the number the better  Digital means sampling (measuring)  where and when that is done  sampling rate  sample resolution (bit depth)  bit rate (for compressed data)  mono vs stereo

... Signal parameters  Signal to noise  ratio of wanted to unwanted sound data  the bigger the number the better

7. Today’s practical

Today’s practical  Aim: to create a set of recordings  to compare equipment and processes with outcomes  to evaluate later (and perhaps to transcribe)  In groups, make a rough plan  roles  what to record  equipment?  When you record  be aware; try to anticipate the result  collect some metadata

8. Defining digital audio

Digital audio AnalogueDigital (identify and measure points)

... Digital audio

Resolution  Sample rate (Hz)  Sample size (bits)  What do they mean?  11KHz, 8 bit  44.1 KHz, 16 bit  48 KHz, 24 bit  192 KHz, 48 bit  Implications for  quality  file size  compatibility, usage...

Encoding  “Codecs”  File formats

9. Compression

 Compression  Reasons  Types  open and proprietary formats (eg MP3 vs ATRAC)  lossy and non-lossy (most are lossy)  repeated compression unpredictable  Remember to distinguish sound information content from its encoding and its carrier Compression

10. Carriers

So you’ve recorded some audio?  Carrier  types  label... or not  preserve  track use of content  You may or may not need to digitise/redigitise/capture it

11. Digitising

Digitising  Where is it actually done?  Involves either  digitisation (capturing/ingesting)  re-digitisation (capturing)  copying (may involve transcoding, e.g. ATRAC)

Digitising  Where were your recordings digitised?

Digitisation: results and quality  What does the result depend on?  player and digitising devices  settings  levels  cables, connections, environment

Digitisation: results and quality  So where can quality be lost?  (ignoring original recording issues)  poor treatment of carriers  unknown properties of carriers (unlabeled etc)  choice of output port, settings (level, format etc)  choice of input port, settings etc  quality of player and digitising devices  connections/cables, interference from other devices or mains supply

Files  Naming  Versions

12. Editing and converting

Editing  Why?  select  modify content  “sweeten” for production  restore, e.g. remove hum, hiss etc.  create products  Software  Audacity, Audition, SoundForge, Peak LE

Converting  Why?  What  Sample rate  Sample size (bit depth)  Encoding  Compression } all different parameters

13. Principles

Some broad principles  Evaluate and compare (use decent closed headphones)  Keep originals at original resolution  Don’t “upsample” or convert compressed material  Understand the basics of the maths, esp files sizes (orders of magnitude!)  Find uses for audio!