1 Audio Recording Techniques 23 June 08 David Nathan Endangered Languages Archive Hans Rausing Endangered Languages Project SOAS, University of London

2 Topics - session 1  Questions  Audio workflow  Evaluating recordings  Perception and psychacoustics  Microphones  Connections  Recorders  Carriers

3 Topics - session 2  Signal parameters  Digital audio  Compression  Digitisation  Files  Editing and conversion  Mobilising audio

4 QUESTIONS

5 Questions (in pairs)  List 3 ways that audio in fieldwork differs from audio in everyday life. -

6 Questions (in pairs)  You buy a recorder for €x. A compatible microphone would cost: (a) 3x (b) 0.75x (c) 0.3x (d) 0.1x (e) none of these - cost is irrelevant

7 Questions (in pairs)  What is the purpose of audio collected in the field?

8 AUDIO WORKFLOW

9 Audio workflow who/what/where /why/how do you want to record? contact people audio training equipment & budget assemble, test, practise Before you go

10 Audio workflow transport safely check environment, situations, permissions make test recordings local training & collaboration On site, before recording

11 Audio workflow record! monitor! collect metadata labelcheck quality monitor Sessions

12 Audio workflow labelcheck quality backupadd information (transcriptions, annotations, metadata etc) After sessions

13 Audio workflow send samples to archive add information (transcriptions, annotations, metadata etc)... package and send to archive Later

14 EVALUATING RECORDINGS

15 Evaluating recordings  signal  noise  signal to noise ratio  listenability (eg comfort, consistency)  fit for purpose

16 Evaluating recordings  (Schüller) audio professionals use the human ear as evaluator of audio value, while many linguists still look to formats, wave-forms etc

17 Signal - what you want  content  fidelity  spatial and contextual information  comfortable to listen to

18 Noise - what you don’t want  from environment:  near: people, animals, activities  far: traffic, generators, planes  machines: refrigerators, fans, computers  not hearable: mobile phones, electrical interference  acoustic: reflections/resonance

19 Noise - what you don’t want  generated by event (unwanted)  shuffling papers, clothes  table banging  backchannel from interviewer  equipment handling, especially microphones and cables

20 Avoiding handling noise  use stands and cradles etc

21 Noise - what you don’t want  generated by equipment  wrong input levels  circuitry noise (cheap or incompatible)  compression loss or distortion  ALC/AGC effects (pumping)  video camera motors

22 Evaluating environment/situation external environment  access  electricity  external noise sources

23 External noise sources examplepossibilities for dealing with it trafficinvestigate, record in quiet time face away use damping materials childrenget them involved show something to satisfy curiosity animalschoose time of day weather (wind, thunder, rain etc) dead cat (windjammer); wait; reschedule  see also General principles

24 Dead cat / Windjammer

25 Close-up noise sources  machines examplepossibilities for dealing with it refrigeratorpre-survey what comes on intermittently turn off relocate motors, switchingmonitor fansmonitor, dead cat (windjammer)

26 Close-up noise sources  be prepared and aware  seek collaboration  monitor  use or modify room acoustics  location  direction  surfaces  reflection  absorption  isolation

27 Room acoustics  location  away from doors, windows, traffic areas  direction  face away from noise sources  surfaces  avoid hard smooth surfaces  reflection  avoid parallel surfaces  absorption  choose or create soft or rough surfaces  isolation  find an ‘’airtight’’ place

28 PERCEPTION & PSYCHOACOUSTICS

29 Human audio perception  a human listener has:  location in physical world  ears - incredibly sensitive  brain/mind  audio information is diverse  the mind merges different kinds of information  listening is largely a “hallucination”  what should we record?  our typical approach to recording is unscientific!

30 Psychoacoustics  microphones are not like camera lenses  will pick up in all directions  don't distinguish wanted and unwanted  recording process removes information  therefore you need to plan and optimise recording

31 “Sound stage”  spatial information is an essential part of audio  we are amazingly attuned to it  we should record in stereo

32 “Sound stage” ... or in ORTF (binaural)

33 MICROPHONES

34 Microphones  microphones in the digital era  comparatively more expensive  recorder quality increase  microphones are analogue!  types  dynamic vs condenser  mono, stereo, binaural  directionality

35 Microphones  dynamic  generate signal from sound pressure  more robust, less accurate  used for musical and live performance  condenser  more sensitive and accurate  need power source - battery or phantom power  in general, use condenser microphones for language documentation

36 Microphones  directionality omni

37 Omni  the most common omni-directional microphones are lavalier or tie-clip microphones

38 Microphones cardioid  directionality

39 Cardioid  many “standard” handheld microphones are cardioid units

40 Microphones directional/ shotgun/ hypercardioid  directionality

41 Shotgun  shotguns are good in noisy environments and for video work

42 ORTF 17cm 110°

43 Microphone usage principles  where should the microphone be?  in general, about 20cm from the speaker’s mouth  the inverse square law is your friend...

44 The inverse square law

45 The inverse square law

46 The inverse square law  if you have noise sources, maximise the signal to noise ratio by placing the microphone as close as possible to the source

47 Microphones - quality  generally, you get what you pay for  decent microphones for field documentation cost from €120 to €400  microphones have their own subjective colour

48 Microphones  placement

49 CONNECTIONS

50 Microphone connections  plugs  cable types  cables for stereo/mono, multiple  wireless  power sources for condenser microphones - battery or phantom power  see

51 Microphone connections  minijack/miniplug (fragile)  RCA/phono  1/4 inch (headphone)  XLR (Canon)

52 XLR  professionals always use XLR  the physical connection is independent of the electrical connection  the latching is independent of the electrical contact  you can use XML to miniplug cables or converters for recorders with miniplug inputs

53 RECORDERS

54 Recorders  types and their strengths/weaknesses/implications  quality parameters  accuracy (freq response, distortion, s/n ratio)  reliability  features  versatility  battery life and power sources

55 Recorders  connections  formats  media types, costs, properties, implications

56 Methods  settings – levels, formats, AGC  a second recorder?  using assistance

57 CARRIERS

58 So you’ve recorded something?  carrier  types  to label... or not  preservation  track the content  you may need to digitise/redigitise/ capture it

59 General guidelines for success  microphone choice  monitoring  familiarity and skill with equipment  power and batteries  a range of equipment, not the “perfect item”!  consistency principle  juxtapositions  efficient field sessions and later processing

60 AUDIO PROPERTIES

61 Audio properties  analogue  digital

62 SIGNAL PARAMETERS

63 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 = 120)  each 6 dB step perceived as doubling/halving volume

64  signal to noise  ratio of wanted to unwanted sound data  the bigger the number the better Signal parameters

65  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

66 DIGITAL AUDIO

67 Digital audio AnalogueDigital (identify and measure points)

68 Digital audio

69 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...

70 Encoding  “codecs”  file formats

71 COMPRESSION

72  reasons  types  open and proprietary formats (eg MP3 vs ATRAC)  lossy and non-lossy (most are lossy)  repeated compression unpredictable  distinguish sound information content from its encoding and its carrier Compression

73 DIGITISATION

74 Digitising  where is it actually done?  involves either  digitisation (capturing/ingesting)  re-digitisation (capturing)  copying (may involve transcoding, e.g. ATRAC)

75 Digitising  Where was your audio digitised?

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

77 Digitisation: results and quality  So where can quality be lost?  (as well as original recording issues)  poor treatment of carriers  unknown properties of carriers (eg unlabeled)  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

78 FILES

79 Files  naming  choose a simple, extendable naming system  do not stuff lots of information into filenames!  - do what instead?  versions  note versions and information about them  designate a definitive version

80 EDITING & CONVERSION

81 Editing  why?  select for transcription, archiving etc  modify content  “sweeten” for production  restore, e.g. remove hum, hiss etc.  create products  software  Audacity, Audition, SoundForge, Peak LE

82 Converting  why?  what  sample rate  sample size (bit depth)  encoding  compression } all different parameters

83 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!

84 MOBILISING AUDIO

85 A paradigm shift?  language documentation does not yet have an epistemology for audio. Linguists remain unclear about:  what is the audio evidence: an event, a recording, sequence of intonation units, file, file + metadata, transcription, a disk?  how to represent and store it  how to present it  what to do with it

86 Advances in audio?  it’s about time that advances and opportunities in audio technology pay out... Edison claimed in 1878 that his phonograph could be used to preserve languages

 Letter writing and all kinds of dictation without the aid of a stenographer  Phonographic books, which speak to blind people...  The teaching of elocution  Reproduction of music  "Family Record“ - a registry of sayings, reminiscences, etc., by members of a family in their own voices, and of the last words of dying persons  Music-boxes and toys  Clocks that should announce in articulate speech the time for going home, going to meals, etc.  The preservation of languages by exact reproduction of the manner of pronouncing  Educational purposes; such as preserving the explanations made by a teacher, so that the pupil can refer to them at any moment, and spelling or other lessons placed upon the phonograph for convenience in committing to memory  Connection with the telephone, so as to make that instrument an auxiliary in the transmission of permanent and invaluable records, instead of being the recipient of momentary and fleeting communication

88 A paradigm shift for audio ?  from evidence to performance…

89 What have we missed?  contact with techniques and experience of established fields e.g.  radio/broadcasting  cinematography  journalism  audio archives  pedagogy

90 Multimedia?

91 Community-oriented multimedia

92 Community-oriented multimedia

93 END !!  This presentation has finished  Good luck making great audio recordings!