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Copyright Tasko & Finan 2008 Instrumentation for “Dummies” Supporting Clinical Practice With Simple, Low-Cost Technology Stephen Tasko Ph.D. CCC-SLP Western.

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Presentation on theme: "Copyright Tasko & Finan 2008 Instrumentation for “Dummies” Supporting Clinical Practice With Simple, Low-Cost Technology Stephen Tasko Ph.D. CCC-SLP Western."— Presentation transcript:

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2 Copyright Tasko & Finan 2008 Instrumentation for “Dummies” Supporting Clinical Practice With Simple, Low-Cost Technology Stephen Tasko Ph.D. CCC-SLP Western Michigan University Kalamazoo MI Donald Finan Ph.D. University of Northern Colorado

3 Copyright Tasko & Finan 2008 Topics Why focus this talk on high quality sound recording? Why focus this talk on high quality sound recording? Sound recording 101 Sound recording 101 Available recording devices Available recording devices

4 Copyright Tasko & Finan 2008 Instrumentation and Technology Love it or hate it?

5 Copyright Tasko & Finan 2008 Why focus discussion on sound recording? High quality digital recordings can now be made with fairly common devices at relatively low costs High quality digital recordings can now be made with fairly common devices at relatively low costs In my view, as both a speech language pathologist and speech scientist, good sound recordings give the SLP the most “bang for the buck” In my view, as both a speech language pathologist and speech scientist, good sound recordings give the SLP the most “bang for the buck”

6 Copyright Tasko & Finan 2008 What high quality digital sound recording offers? Provides a permanent archive of client behavior Provides a permanent archive of client behavior Can allow quick, easy access to samples to monitor client status Can allow quick, easy access to samples to monitor client status Has face validity Has face validity Potential for more objective baseline and follow up evaluation Potential for more objective baseline and follow up evaluation Can support and guide clinical decision making Can support and guide clinical decision making Can serve to streamline and standardize assessment approaches Can serve to streamline and standardize assessment approaches Allows an entrée into Allows an entrée into More quantitative instrumented analysis More quantitative instrumented analysis Database development for clinician directed research on outcomes Database development for clinician directed research on outcomes

7 Copyright Tasko & Finan 2008 Sound Recording 101

8 Copyright Tasko & Finan 2008 Tasko’s rating system Preferable Highly preferred Not recommended Strongly discouraged

9 Copyright Tasko & Finan 2008 Sound Frequency ranges Normal humans hearing 20 Hz – 20,000 Hz Normal humans hearing 20 Hz – 20,000 Hz Human speech ~ 50 Hz – 8000 Hz Human speech ~ 50 Hz – 8000 Hz Standard phone circuits ~ Hz Standard phone circuits ~ Hz

10 Copyright Tasko & Finan 2008 Frequency Range for Speech For good audibility, we need to be sure our recordings capture the whole frequency range for speech

11 Copyright Tasko & Finan 2008 What are you using the recording for?

12 Copyright Tasko & Finan 2008 Components of Sound Recording microphone Pre-amplifier (maybe) Cassette recorder

13 Copyright Tasko & Finan 2008 Components of Sound Recording microphone Pre-amplifier (maybe) or

14 Copyright Tasko & Finan 2008 The quality of the recording is only as good as its weakest component

15 Copyright Tasko & Finan 2008 Components of Sound Recording Microphone Digital Recording Device Digitization of sound Storing of sound as file Playback ability Amplifier-Speaker Headset +/- amplifier

16 Copyright Tasko & Finan 2008 How does tape recording differ from digital recording? Analog (tape) recording Analog (tape) recording Acquires a continuously varying signal Acquires a continuously varying signal Digital recording Digital recording Acquires a string of discrete numbers Acquires a string of discrete numbers

17 Copyright Tasko & Finan 2008 Analog (Continuous) Digital (Discrete)

18 Copyright Tasko & Finan 2008 Digital Recording Since sound is converted to a string of numbers, two issues have an influence on recording accuracy/fidelity 1. How often does the device “grab” a number? Sampling rate/frequency 2. How much precision is used when number recording? Quantization level

19 Copyright Tasko & Finan 2008 Sampling Rate High Low

20 Copyright Tasko & Finan 2008 Sampling Theorem If a band-limited signal is sampled at a rate that is at least twice as high as the highest frequency in the signal, no information is lost and the original signal can be exactly reconstructed from the samples

21 Copyright Tasko & Finan 2008 Nyquist frequency Maximum frequency contained in the signal of interest Maximum frequency contained in the signal of interest Humans hear < 20 KHz Humans hear < 20 KHz Human speech < 7-8 KHz Human speech < 7-8 KHz Phone circuits < 3.2 KHz Phone circuits < 3.2 KHz

22 Copyright Tasko & Finan 2008 Simple Rule sample rate/frequency must be 2X highest frequency of interest For speech it must be at least Hz

23 Copyright Tasko & Finan 2008 Digital Devices: Common sample rates 5,562 Hz 5,562 Hz 11,025 Hz 11,025 Hz 22,050 Hz 22,050 Hz 44,100 Hz 44,100 Hz CD quality CD quality Captures range of hearing Captures range of hearing 16 KHz 32 KHz 8 KHz 4 KHz 2 KHz

24 Copyright Tasko & Finan 2008 Loosing important parts of the “bandwidth” Loosing important parts of the “bandwidth” Possibility of “aliasing” Possibility of “aliasing” Most sound cards have anti-aliasing filters Most sound cards have anti-aliasing filters Low-pass filters sound to prevent aliasing Low-pass filters sound to prevent aliasing However, now have a restricted bandwidth However, now have a restricted bandwidth TAKE-HOME MESSAGE DO NOT UNDERSAMPLE YOUR SIGNAL Problems associated with poor selection of sample rate F= 7 KHz SF=16KHz F=7 KHz SF=8 KHz

25 Copyright Tasko & Finan 2008 Quantization Inches less precise millimeters more precise

26 Copyright Tasko & Finan 2008 Quantization High Low

27 Copyright Tasko & Finan 2008 Quantization Expressed in “bits” Expressed in “bits” ↑ bits ~ ↑ # of marks on the “ruler” = greater precision ↑ bits ~ ↑ # of marks on the “ruler” = greater precision X bits/sample = 2 x possible units of measure X bits/sample = 2 x possible units of measure For example, For example, 2 bit = 4 levels 2 bit = 4 levels 4 bit = 16 levels 4 bit = 16 levels 8 bit = 256 levels 8 bit = 256 levels 12 bit=4096 levels 12 bit=4096 levels 16 bit = levels 16 bit = levels

28 Copyright Tasko & Finan 2008 Quantization Expressed in “bits” Expressed in “bits” ↑ bits ~ ↑ # of marks on the “ruler” = greater precision ↑ bits ~ ↑ # of marks on the “ruler” = greater precision X bits/sample = 2 x possible units of measure X bits/sample = 2 x possible units of measure For example, For example, 2 bit = 4 levels 2 bit = 4 levels 4 bit = 16 levels 4 bit = 16 levels 8 bit = 256 levels 8 bit = 256 levels 12 bit=4096 levels 12 bit=4096 levels 16 bit = levels 16 bit = levels

29 Low sampling rate Low quantization Low sampling rate High quantization High sampling rate Low quantization

30 Copyright Tasko & Finan 2008 Checking your own computer

31 Copyright Tasko & Finan 2008 Sound Fidelity vs. File Size Digital memory is relatively cheap Digital memory is relatively cheap Good client records are invaluable Good client records are invaluable

32 Copyright Tasko & Finan 2008 Components of Sound Recording Microphone Digital Recording Device Digitization of sound Storing of sound as file Playback ability Amplifier-Speaker Headset +/- amplifier

33 Copyright Tasko & Finan 2008 Digital File formats Mono vs. Stereo Mono vs. Stereo Alphabet Soup Alphabet Soup.wav.wav.nsp.nsp.mp3.mp3.mp4.mp4.wma.wma.dss.dss.au.au etc, etc, etc etc, etc, etc

34 Copyright Tasko & Finan 2008 Digital File formats Uncompressed Formats (Lossless) All samples are retained All samples are retained What you record is what you get What you record is what you get Most common format Most common format “.wav” (PCM) “.wav” (PCM) Compressed Formats algorithm used to reduce file size yet maintain good audibility algorithm used to reduce file size yet maintain good audibility Driven, in part, by music industry Driven, in part, by music industry Common Formats Common Formats.mp3,.wma,.dss Effect on speech samples is not well known Effect on speech samples is not well known

35 Copyright Tasko & Finan 2008 Components of Sound Recording Microphone Digital Recording Device Digitization of sound Storing of sound as file Playback ability Amplifier-Speaker Headset +/- amplifier

36 Copyright Tasko & Finan 2008 The Microphone Microphones Matter!!

37 Copyright Tasko & Finan 2008 What (I think) you need to know about microphone selection Type of microphone Type of microphone Underlying operation Underlying operation How it connects to other devices How it connects to other devices Pick up patterns Pick up patterns Frequency Response Frequency Response

38 Copyright Tasko & Finan 2008 Microphones: Common Types Handheld Built in to recorder Clip on/lavalier Head worn

39 Copyright Tasko & Finan 2008 Underlying operation

40 Copyright Tasko & Finan 2008

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43 Headset Microphone Placement

44 Copyright Tasko & Finan 2008 Microphone Frequency Response What is a frequency response curve? What is a frequency response curve? Graph that shows how the microphone responds over a range of frequencies Graph that shows how the microphone responds over a range of frequencies Look for a relatively flat line within the frequency range for speech Look for a relatively flat line within the frequency range for speech

45 Copyright Tasko & Finan 2008 Frequency Response Curve

46 Copyright Tasko & Finan 2008 Frequency Response Curve Speech Range

47 Copyright Tasko & Finan 2008 Frequency Response Curve

48 Copyright Tasko & Finan 2008 To pre-amplify or not to pre-amplify Great variation in size of signal coming from mics Great variation in size of signal coming from mics May need to amplify the mic signal so it is heard by the recording device May need to amplify the mic signal so it is heard by the recording device Often Often Best mics put out small signals Best mics put out small signals Cheapest mics put out largest signals Cheapest mics put out largest signals

49 Copyright Tasko & Finan 2008 A Tasko Seal of Approval Audio-Technica ATM75 (without powerpack!! - cheaper) Audio-Technica ATM75 (without powerpack!! - cheaper)Features Condensor type Headworn Condensor type Headworn Directional Directional Acceptable frequency response Acceptable frequency response Decent sized output signal Decent sized output signal amplification not typically necessary amplification not typically necessary Can be purchased with a variety of connectors Can be purchased with a variety of connectors REASONABLY PRICED (~ $99) REASONABLY PRICED (~ $99)

50 Copyright Tasko & Finan 2008 Audio Technica ATM75

51 Copyright Tasko & Finan 2008 Recording Issues Keep mic-mouth distance relatively constant within and across recording sessions Keep mic-mouth distance relatively constant within and across recording sessions Setting your recording levels is very important Setting your recording levels is very important You really want a device that monitors the recording level You really want a device that monitors the recording level

52 Copyright Tasko & Finan 2008 Apply the “Goldilocks” Rule

53 Copyright Tasko & Finan 2008 That recording level is just tooooo low! Environmental noise becomes an issue Environmental noise becomes an issue Does not take advantage of the precision of the recording device Does not take advantage of the precision of the recording device

54 Copyright Tasko & Finan 2008 That recording level is just tooooo high! Signal will be “clipped” resulting in distortion Signal will be “clipped” resulting in distortion Truncates the largest amplitude components Truncates the largest amplitude components

55 Copyright Tasko & Finan 2008 Components of Sound Recording Microphone Digital Recording Device Digitization of sound Storing of sound as file Playback ability Amplifier-Speaker Headset +/- amplifier

56 Copyright Tasko & Finan 2008 A brief survey of digital recording devices Personal Recording Devices Personal Recording Devices Digital dictaphones Digital dictaphones iPods iPods PDAs (Palms, Smartphones) PDAs (Palms, Smartphones) “Professional” Grade Devices “Professional” Grade Devices Digital equivalents to the pro-duty cassette recorders Digital equivalents to the pro-duty cassette recorders Devices developed primarily for music industry Devices developed primarily for music industry The PC (or Mac) The PC (or Mac) Laptop Laptop Desktop Desktop

57 Copyright Tasko & Finan 2008 Questions to ask about portable recording devices Basic recording performance questions Are the sampling rate options appropriate for speech recording? Are the sampling rate options appropriate for speech recording? Is the quantization rate appropriate for speech recording? Is the quantization rate appropriate for speech recording? Is the overall frequency response of the device acceptable for speech recording? Is the overall frequency response of the device acceptable for speech recording?

58 Copyright Tasko & Finan 2008 Questions to ask about portable recording devices Microphone/recording level related questions Can an external microphone be used? Can an external microphone be used? What kind of connectors are needed? What kind of connectors are needed? Will you need a mic amplifier? Will you need a mic amplifier? Can recording levels be adjusted? Can recording levels be adjusted? Can recording levels be monitored? Can recording levels be monitored?

59 Copyright Tasko & Finan 2008 Questions to ask about portable recording devices Data Storage/Transfer Questions What file format is used to save the data? What file format is used to save the data? Can it record in a lossless format? Can it record in a lossless format? What is the recording capacity of the system with the preferred recording settings? What is the recording capacity of the system with the preferred recording settings? Does it have only built in memory or can you use standard memory media (e.g. SD cards)? Does it have only built in memory or can you use standard memory media (e.g. SD cards)? How easy is it to move the recordings off the device and onto a PC for archiving (i.e. USB)? How easy is it to move the recordings off the device and onto a PC for archiving (i.e. USB)?

60 Copyright Tasko & Finan 2008 Questions to ask about portable recording devices Human Factors Questions Can you easily play back recordings? Can you easily play back recordings? What is quality of device playback? What is quality of device playback? Is it easy to use? Is it easy to use? Is it too big or small? Is it too big or small? …

61 Copyright Tasko & Finan 2008 Personal Recording Devices Digital dictaphones Digital dictaphones iPods iPods PDAs (Palms, Smartphones) PDAs (Palms, Smartphones) Many have good specifications Many have good specifications File format options can be quite limited File format options can be quite limited Often have serious limitations regarding microphone/recording level flexibility Often have serious limitations regarding microphone/recording level flexibility

62 Copyright Tasko & Finan 2008 Dictaphones

63 Other options: iPod

64 Copyright Tasko & Finan 2008 Personal Recording Devices

65 Copyright Tasko & Finan 2008 “Professional” Grade Devices Greater flexibility in all areas Greater flexibility in all areas Minimize concerns about digitization specs Minimize concerns about digitization specs Typically use a.wav (uncompressed) format Typically use a.wav (uncompressed) format Larger and sometimes bulky Larger and sometimes bulky Can be quite expensive Can be quite expensive Good values if you look at devices designed for the music industry Good values if you look at devices designed for the music industry

66 Copyright Tasko & Finan 2008 Professional Duty Marantz PMD660 ~ $500

67 Copyright Tasko & Finan 2008 Professional Duty Boss Micro BR ~ $230 Don Finan’s Seal Of Approval

68 Copyright Tasko & Finan 2008 Professional Duty M-Audio Microtrack < $300

69 Copyright Tasko & Finan 2008 A Significant Disadvantage of Recording with Portable Devices ↑↑ Housekeeping duties ↑↑ Housekeeping duties Sound recording file management Sound recording file management Naming files so you know what is in them Naming files so you know what is in them Moving files from device or portable media to a more permanent archive (PC, CD) Moving files from device or portable media to a more permanent archive (PC, CD) Finding software to replay the files you’ve acquired Finding software to replay the files you’ve acquired

70 Copyright Tasko & Finan 2008 PC Based Recording

71 Copyright Tasko & Finan 2008 Free (yes, free) software for recording/analyzing high quality speech signals Speech Tool Speech Tool SFSWin (UCL Phonetics Lab) SFSWin (UCL Phonetics Lab) Alvin Alvin Wavesurfer Wavesurfer Praat Praat Audacity Audacity

72 Copyright Tasko & Finan 2008 Issues with PC recording Not all PC sound cards are identical Not all PC sound cards are identical Vast majority work perfectly well Vast majority work perfectly well Occasional problems include Occasional problems include Noise or static Noise or static Shifts in recording baseline (does not affect how it sound) Shifts in recording baseline (does not affect how it sound)


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