Audio Recording Techniques 23 June 08

1. Audio Recording Techniques23 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 Before you go who/what/where /why/how do you want to record? contact people audio training equipment & budget assemble, test, practise

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

11. Audio workflow Sessions monitor record! monitor! collect metadata label check quality

12. Audio workflow After sessions label check quality backup add information (transcriptions, annotations, metadata etc)

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

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 • see also General principles

24. Dead cat / Windjammer

25. Close-up noise sources • machines

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 notlike 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 110° 17cm

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 http://www.hrelp.org/archive/advice/microphones.html