Audio Recording Techniques & Equipment - PowerPoint PPT Presentation

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  1. Audio Recording Techniques & Equipment Saami Winter School Feb 10 Bodø, Norway 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. QUESTIONS

  4. Questions • You buy a recorder for $x. A matching microphone would cost: (a) 3x (b) 0.75x (c) 0.3x (d) 0.1x (e) none of these - cost is irrelevant

  5. Big questions • What are we actually recording? • What is it for? • What is the role of audio in language documentation?

  6. What is audio? • Audio is not data • real world • record phenomena • represent phenomena • derive data • Audio is a resource • making it is both art and science • a critical and ethical responsibility • strongest relationship to communities • it’s not necessary to record everything, but it is neceessary to record well

  7. AUDIO WORKFLOW

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

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

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

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

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

  13. EVALUATING RECORDINGS

  14. Evaluating recordings • signal • noise • signal to noise ratio • listenability (eg comfort, consistency) • fit for purpose

  15. Evaluating recordings • audio professionals use the human ear as evaluator of audio quality and value, while many linguists mistakenly look to formats, wave-forms, analyses etc   44.1 KHz, 24 bit

  16. Signal - what you want • content • contextual and spatial information • fidelity • comfortable to listen to

  17. 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

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

  19. Avoiding handling noise • use stands and cradles etc

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

  21. Evaluating environment/situation external environment • access • electricity • external noise sources

  22. External noise sources • see also General principles

  23. Dead cat

  24. Close-up noise sources • machines

  25. Dealing with noise sources • be prepared and aware • seek collaboration • monitor • use or modify room acoustics • location • direction • surfaces • reflection • absorption • isolation

  26. 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

  27. PERCEPTION & PSYCHOACOUSTICS

  28. Audio perception/psychoacoustics • audio information is diverse • a human listener has: • location and orientation in physical world • two ears - which are incredibly sensitive • a brain/mind • the mind merges and selects from various sources of audio information • listening is actually a “hallucination” • so what should we record? • typical recording methods are unscientific!

  29. Psychoacoustics and recording • microphones are notlike camera lenses • they don’t have “edges” • don't distinguish wanted and unwanted info • the recording process removes some information

  30. Implications for recording • you need to set goals, plan and manage recording • goals • equipment • sources • environment • settings • example: recording spatial information • why is this important?

  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 and audio quality • microphones are the greatest determinant of audio recording quality • selection of appropriate microphone(s) for the task • placement and handling of the microphone(s)

  35. Microphones in the digital era • microphones in the digital era • recorder quality has increased but prices decreased • microphones have become comparatively more expensive • why? microphones are analogue devices!

  36. Microphone types • principle: dynamic vs condenser • directionality: omni, cardoid, and shotgun • spatiality: mono, stereo, binaural

  37. Microphone physical principles • dynamic • generate signal from sound pressure • more robust, less accurate • used for musical and live performance • condenser • more fragile, sensitive and accurate • need power source - battery or phantom power • in general, use condenser microphones for language documentation

  38. Microphone directionality - omni omni

  39. Omni • lavalier or tie-clip microphones are typically omni-directional

  40. Microphone directionality - cardioid cardioid

  41. Cardioid • many “standard” handheld microphones are cardioid units

  42. Microphone directionality - shotgun directional/shotgun/hypercardioid

  43. Shotgun • shotguns are good for quiet sources, in some noisy environments, and for video work

  44. Stereo microphones • spatial information is an essential part of audio

  45. Full “sound stage”: ORTF

  46. 110° 17cm Simulating ORTF with 2 cardioids

  47. Microphones - quality • generally, you get what you pay for • each model has its own subjective colour • decent microphones for language documentation fieldwork cost from £120 to £300

  48. Reputable makers - include • AKG • Audio Technica • Beyerdynamic • Røde • Sennheiser • Shure • Sony

  49. Microphone placement

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