copyright tasko & finan 2008 instrumentation for “dummies” supporting clinical practice with...
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Copyright Tasko & Finan 2008Copyright Tasko & Finan 2008
Instrumentation for Instrumentation for “Dummies”“Dummies”
Supporting Clinical Practice Supporting Clinical Practice With Simple, Low-Cost With Simple, Low-Cost
TechnologyTechnology
Stephen Tasko Ph.D. CCC-SLPWestern Michigan UniversityKalamazoo MI
Donald Finan Ph.D.University of Northern Colorado
http://homepages.wmich.edu/~staskohttp://homepages.wmich.edu/~stasko
Copyright Tasko & Finan 2008Copyright Tasko & Finan 2008
TopicsTopics
Why focus this talk on high quality sound Why focus this talk on high quality sound recording?recording?
Sound recording 101Sound recording 101
Available recording devicesAvailable recording devices
Copyright Tasko & Finan 2008Copyright Tasko & Finan 2008
Instrumentation and Instrumentation and TechnologyTechnology
Love it or hate it?Love it or hate it?
Copyright Tasko & Finan 2008Copyright Tasko & Finan 2008
Why focus discussion on sound Why focus discussion on sound recording?recording?
High quality digital recordings can now be High quality digital recordings can now be made with fairly common devices at made with fairly common devices at relatively low costsrelatively low costs
In my view, as both a speech language In my view, as both a speech language pathologist and speech scientist, good pathologist and speech scientist, good sound recordings give the SLP the most sound recordings give the SLP the most “bang for the buck”“bang for the buck”
Copyright Tasko & Finan 2008Copyright Tasko & Finan 2008
What high quality digital sound What high quality digital sound recording offers?recording offers?
Provides a permanent archive of client behaviorProvides a permanent archive of client behavior Can allow quick, easy access to samples to monitor Can allow quick, easy access to samples to monitor
client statusclient status Has face validityHas face validity Potential for more objective baseline and follow up Potential for more objective baseline and follow up
evaluationevaluation Can support and guide clinical decision makingCan support and guide clinical decision making Can serve to streamline and standardize assessment Can serve to streamline and standardize assessment
approaches approaches Allows an entrée intoAllows an entrée into
More quantitative instrumented analysisMore quantitative instrumented analysis Database development for clinician directed research on Database development for clinician directed research on
outcomesoutcomes
Copyright Tasko & Finan 2008Copyright Tasko & Finan 2008
Tasko’s rating systemTasko’s rating system
PreferablePreferable
Highly preferredHighly preferred
Not recommendedNot recommended
Strongly discouragedStrongly discouraged
Copyright Tasko & Finan 2008Copyright Tasko & Finan 2008
Sound Frequency rangesSound Frequency ranges
Normal humans hearing 20 Hz – 20,000 HzNormal humans hearing 20 Hz – 20,000 Hz
Human speech ~ 50 Hz – 8000 HzHuman speech ~ 50 Hz – 8000 Hz
Standard phone circuits ~ 300 - 3000 HzStandard phone circuits ~ 300 - 3000 Hz
Copyright Tasko & Finan 2008Copyright Tasko & Finan 2008
Frequency Range for SpeechFrequency Range for Speech
For good audibility, we need to be sure our recordings capture the whole frequency range for speech
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What are you using the What are you using the recording for?recording for?
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Components of Sound RecordingComponents of Sound Recording
microphone Pre-amplifier(maybe)
Cassette recorder
Copyright Tasko & Finan 2008Copyright Tasko & Finan 2008
Components of Sound RecordingComponents of Sound Recording
microphone Pre-amplifier(maybe)
or
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The quality of the recording is The quality of the recording is only as good as its weakest only as good as its weakest
componentcomponent
Copyright Tasko & Finan 2008Copyright Tasko & Finan 2008
Components of Sound RecordingComponents of Sound Recording
Microphone
Digital Recording Device•Digitization of sound•Storing of sound as file
Playback ability•Amplifier-Speaker•Headset
+/- amplifier
Copyright Tasko & Finan 2008Copyright Tasko & Finan 2008
How does tape recording differ How does tape recording differ from digital recording?from digital recording?
Analog (tape) recordingAnalog (tape) recordingAcquires a continuously varying signalAcquires a continuously varying signal
Digital recordingDigital recordingAcquires a string of discrete numbersAcquires a string of discrete numbers
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Analog (Continuous)
Digital (Discrete)
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Digital RecordingDigital Recording
Since sound is converted to a string of numbers, Since sound is converted to a string of numbers, two issues have an influence on recording two issues have an influence on recording
accuracy/fidelityaccuracy/fidelity
1. How often does the device “grab” a number? 1. How often does the device “grab” a number? Sampling rate/frequencySampling rate/frequency
2. How much precision is used when number 2. How much precision is used when number recording?recording?Quantization levelQuantization level
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Sampling Rate
High
Low
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Sampling TheoremSampling Theorem
If a band-limited signal is sampled at a rate If a band-limited signal is sampled at a rate that is at least twice as high as the highest that is at least twice as high as the highest frequency in the signal, no information is frequency in the signal, no information is lost and the original signal can be exactly lost and the original signal can be exactly reconstructed from the samplesreconstructed from the samples
Copyright Tasko & Finan 2008Copyright Tasko & Finan 2008
Nyquist frequencyNyquist frequency
Maximum frequency contained in the Maximum frequency contained in the signal of interestsignal of interest
Humans hear < 20 KHzHumans hear < 20 KHzHuman speech < 7-8 KHzHuman speech < 7-8 KHzPhone circuits < 3.2 KHzPhone circuits < 3.2 KHz
Copyright Tasko & Finan 2008Copyright Tasko & Finan 2008
Simple RuleSimple Rule
sample rate/frequency must be 2X highest frequency of interest
For speech it must be at least 16000 Hz
Copyright Tasko & Finan 2008Copyright Tasko & Finan 2008
Digital Devices: Common sample ratesDigital Devices: Common sample rates
5,562 Hz5,562 Hz
11,025 Hz11,025 Hz
22,050 Hz22,050 Hz
44,100 Hz44,100 Hz CD qualityCD quality Captures range of hearing Captures range of hearing
16 KHz
32 KHz
8 KHz
4 KHz
2 KHz
Copyright Tasko & Finan 2008Copyright 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 aliasingLow-pass filters sound to prevent aliasing However, now have a restricted bandwidthHowever, now have a restricted bandwidth
TAKE-HOME MESSAGETAKE-HOME MESSAGEDO NOT UNDERSAMPLE YOUR SIGNALDO NOT UNDERSAMPLE YOUR SIGNAL
Problems associated with poor Problems associated with poor selection of sample rateselection of sample rate
http://www.dsptutor.freeuk.com/aliasing/AliasingDemo.html
F= 7 KHzSF=16KHz
F=7 KHzSF=8 KHz
Copyright Tasko & Finan 2008Copyright Tasko & Finan 2008
QuantizationQuantization
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millimetersmore precise
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Quantization
High
Low
Copyright Tasko & Finan 2008Copyright Tasko & Finan 2008
QuantizationQuantization
Expressed in “bits”Expressed in “bits” ↑↑ bits ~ bits ~ ↑↑ # of marks on the “ruler” = greater precision # of marks on the “ruler” = greater precision X bits/sample = 2X bits/sample = 2x x possible units of measurepossible units of measure For example,For example,
2 bit = 4 levels2 bit = 4 levels 4 bit = 16 levels4 bit = 16 levels 8 bit = 256 levels8 bit = 256 levels 12 bit=4096 levels12 bit=4096 levels 16 bit = 65536 levels16 bit = 65536 levels
http://www.cosc.canterbury.ac.nz/mukundan/covn/Quant.html
Copyright Tasko & Finan 2008Copyright Tasko & Finan 2008
QuantizationQuantization
Expressed in “bits”Expressed in “bits” ↑↑ bits ~ bits ~ ↑↑ # of marks on the “ruler” = greater precision # of marks on the “ruler” = greater precision X bits/sample = 2X bits/sample = 2x x possible units of measurepossible units of measure For example,For example,
2 bit = 4 levels2 bit = 4 levels 4 bit = 16 levels4 bit = 16 levels 8 bit = 256 levels8 bit = 256 levels 12 bit=4096 levels12 bit=4096 levels 16 bit = 65536 levels 16 bit = 65536 levels
Copyright Tasko & Finan 2008Copyright Tasko & Finan 2008
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00.250.50.7511.251.51.7522.252.52.7533.253.53.7544.254.54.7555.255.55.7566.256.56.7577.257.57.7588.258.58.7599.259.59.751010.2510.510.751111.2511.511.751212.2512.512.751313.2513.513.751414.2514.514.751515.2515.515.751616.2516.516.751717.2517.517.751818.2518.518.751919.2519.519.7520-2
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Low sampling rate
Low quantization
Low sampling rate
High quantization
High sampling rate
Low quantization
Copyright Tasko & Finan 2008Copyright Tasko & Finan 2008
Checking your own computerChecking your own computer
Copyright Tasko & Finan 2008Copyright Tasko & Finan 2008
Sound Fidelity vs. File SizeSound Fidelity vs. File Size
Digital memory is relatively cheapDigital memory is relatively cheap Good client records are invaluableGood client records are invaluable
Copyright Tasko & Finan 2008Copyright Tasko & Finan 2008
Components of Sound RecordingComponents of Sound Recording
Microphone
Digital Recording Device•Digitization of sound•Storing of sound as file
Playback ability•Amplifier-Speaker•Headset
+/- amplifier
Copyright Tasko & Finan 2008Copyright Tasko & Finan 2008
Digital File formatsDigital File formats
Mono vs. StereoMono vs. Stereo Alphabet SoupAlphabet Soup
.wav.wav .nsp.nsp .mp3.mp3 .mp4.mp4 .wma.wma .dss.dss .au.au etc, etc, etcetc, etc, etc
Copyright Tasko & Finan 2008Copyright Tasko & Finan 2008
Digital File formatsDigital File formats
Uncompressed Formats Uncompressed Formats (Lossless)(Lossless)
All samples are retainedAll samples are retained What you record is what What you record is what
you getyou get Most common formatMost common format
““.wav” (PCM).wav” (PCM)
Compressed FormatsCompressed Formats algorithm used to reduce algorithm used to reduce
file size yet maintain good file size yet maintain good audibilityaudibility
Driven, in part, by music Driven, in part, by music industryindustry
Common FormatsCommon Formats .mp3, .wma, .dss.mp3, .wma, .dss
Effect on speech samples Effect on speech samples is not well knownis not well known
Copyright Tasko & Finan 2008Copyright Tasko & Finan 2008
Components of Sound RecordingComponents of Sound Recording
Microphone
Digital Recording Device•Digitization of sound•Storing of sound as file
Playback ability•Amplifier-Speaker•Headset
+/- amplifier
Copyright Tasko & Finan 2008Copyright Tasko & Finan 2008
The MicrophoneThe Microphone
Microphones Microphones Matter!!Matter!!
Copyright Tasko & Finan 2008Copyright Tasko & Finan 2008
What (I think) you need to know What (I think) you need to know about microphone selectionabout microphone selection
Type of microphoneType of microphone
Underlying operationUnderlying operation
How it connects to other devicesHow it connects to other devices
Pick up patternsPick up patterns
Frequency ResponseFrequency Response
Copyright Tasko & Finan 2008Copyright Tasko & Finan 2008
Microphones: Common TypesMicrophones: Common Types
HandheldHandheld
Built in to recorderBuilt in to recorder
Clip on/lavalierClip on/lavalierHead wornHead worn
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Headset Microphone PlacementHeadset Microphone Placement
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Microphone Frequency ResponseMicrophone Frequency Response
What is a frequency response curve?What is a frequency response curve?Graph that shows how the microphone Graph that shows how the microphone
responds over a range of frequenciesresponds over a range of frequenciesLook for a relatively flat line within the Look for a relatively flat line within the
frequency range for speechfrequency range for speech
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Frequency Response CurveFrequency Response Curve
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Frequency Response CurveFrequency Response Curve
Speech Range
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Frequency Response CurveFrequency Response Curve
Copyright Tasko & Finan 2008Copyright Tasko & Finan 2008
To pre-amplify or not to pre-amplifyTo pre-amplify or not to pre-amplify
Great variation in size of Great variation in size of signal coming from micssignal coming from mics
May need to amplify the May need to amplify the mic signal so it is heard mic signal so it is heard by the recording deviceby the recording device
OftenOften Best mics put out small Best mics put out small
signalssignals Cheapest mics put out Cheapest mics put out
largest signalslargest signals
Copyright Tasko & Finan 2008Copyright Tasko & Finan 2008
A Tasko Seal of ApprovalA Tasko Seal of Approval
Audio-Technica ATM75 (without powerpack!! - cheaper)Audio-Technica ATM75 (without powerpack!! - cheaper)
FeaturesFeatures Condensor type HeadwornCondensor type Headworn DirectionalDirectional Acceptable frequency responseAcceptable frequency response Decent sized output signalDecent sized output signal
amplification not typically necessaryamplification not typically necessary Can be purchased with a variety of connectorsCan be purchased with a variety of connectors REASONABLY PRICED (~ $99)REASONABLY PRICED (~ $99)
Copyright Tasko & Finan 2008Copyright Tasko & Finan 2008
Audio Technica ATM75Audio Technica ATM75
http://www.soundprofessionals.com/cgi-bin/gold/item/ATM75-SP-NP
Copyright Tasko & Finan 2008Copyright Tasko & Finan 2008
Recording IssuesRecording Issues
Keep mic-mouth distance relatively Keep mic-mouth distance relatively constant within and across recording constant within and across recording sessionssessions
Setting your recording levels is very Setting your recording levels is very importantimportant
You really want a device that monitors the You really want a device that monitors the recording levelrecording level
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Apply the “Goldilocks” RuleApply the “Goldilocks” Rule
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That recording level is just tooooo low!That recording level is just tooooo low!
Environmental noise becomes an issueEnvironmental noise becomes an issueDoes not take advantage of the precision Does not take advantage of the precision
of the recording deviceof the recording device
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That recording level is just tooooo high!That recording level is just tooooo high!
Signal will be “clipped” resulting in distortionSignal will be “clipped” resulting in distortionTruncates the largest amplitude Truncates the largest amplitude
componentscomponents
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Copyright Tasko & Finan 2008Copyright Tasko & Finan 2008
Components of Sound RecordingComponents of Sound Recording
Microphone
Digital Recording Device•Digitization of sound•Storing of sound as file
Playback ability•Amplifier-Speaker•Headset
+/- amplifier
Copyright Tasko & Finan 2008Copyright Tasko & Finan 2008
A brief survey of digital recording A brief survey of digital recording devicesdevices
Personal Recording DevicesPersonal Recording Devices Digital dictaphonesDigital dictaphones iPodsiPods PDAs (Palms, Smartphones) PDAs (Palms, Smartphones)
““Professional” Grade DevicesProfessional” Grade Devices Digital equivalents to the pro-duty cassette recordersDigital equivalents to the pro-duty cassette recorders Devices developed primarily for music industryDevices developed primarily for music industry
The PC (or Mac)The PC (or Mac) LaptopLaptop DesktopDesktop
Copyright Tasko & Finan 2008Copyright Tasko & Finan 2008
Questions to ask about portable Questions to ask about portable recording devicesrecording devices
Basic recording performance questionsBasic recording performance questionsAre the sampling rate options appropriate Are the sampling rate options appropriate
for speech recording?for speech recording? Is the quantization rate appropriate for Is the quantization rate appropriate for
speech recording?speech recording? Is the overall frequency response of the Is the overall frequency response of the
device acceptable for speech recording?device acceptable for speech recording?
Copyright Tasko & Finan 2008Copyright Tasko & Finan 2008
Questions to ask about portable Questions to ask about portable recording devicesrecording devices
Microphone/recording level related questionsMicrophone/recording level related questionsCan 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?
Copyright Tasko & Finan 2008Copyright Tasko & Finan 2008
Questions to ask about portable Questions to ask about portable recording devicesrecording devices
Data Storage/Transfer QuestionsData 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 What is the recording capacity of the system
with the preferred recording settings?with the preferred recording settings? Does it have only built in memory or can you use Does it have only built in memory or can you use
standard memory media (e.g. SD cards)?standard memory media (e.g. SD cards)? How easy is it to move the recordings off the How easy is it to move the recordings off the
device and onto a PC for archiving (i.e. USB)?device and onto a PC for archiving (i.e. USB)?
Copyright Tasko & Finan 2008Copyright Tasko & Finan 2008
Questions to ask about portable Questions to ask about portable recording devicesrecording devices
Human Factors QuestionsHuman Factors QuestionsCan 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?……
Copyright Tasko & Finan 2008Copyright Tasko & Finan 2008
Personal Recording DevicesPersonal Recording Devices
Digital dictaphonesDigital dictaphones iPodsiPodsPDAs (Palms, Smartphones)PDAs (Palms, Smartphones)
Many have good specificationsMany have good specificationsFile format options can be quite limitedFile format options can be quite limitedOften have serious limitations regarding Often have serious limitations regarding
microphone/recording level flexibilitymicrophone/recording level flexibility
Copyright Tasko & Finan 2008Copyright Tasko & Finan 2008
Personal Recording DevicesPersonal Recording Devices
Copyright Tasko & Finan 2008Copyright Tasko & Finan 2008
““Professional” Grade DevicesProfessional” Grade Devices
Greater flexibility in all areasGreater flexibility in all areasMinimize concerns about digitization specsMinimize concerns about digitization specsTypically use a .wav (uncompressed) formatTypically use a .wav (uncompressed) formatLarger and sometimes bulkyLarger and sometimes bulkyCan be quite expensiveCan be quite expensiveGood values if you look at devices designed Good values if you look at devices designed
for the music industryfor the music industry
Copyright Tasko & Finan 2008Copyright Tasko & Finan 2008
Professional DutyProfessional Duty
Marantz PMD660Marantz PMD660~ $500~ $500
Copyright Tasko & Finan 2008Copyright Tasko & Finan 2008
Professional DutyProfessional Duty
Boss Micro BRBoss Micro BR~ $230~ $230
Don Finan’s SealDon Finan’s SealOf ApprovalOf Approval
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Professional DutyProfessional Duty
M-Audio MicrotrackM-Audio Microtrack< $300< $300
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A Significant Disadvantage of A Significant Disadvantage of Recording with Portable DevicesRecording with Portable Devices
↑↑ ↑↑ Housekeeping dutiesHousekeeping dutiesSound recording file managementSound recording file managementNaming files so you know what is in themNaming files so you know what is in themMoving files from device or portable media to Moving files from device or portable media to
a more permanent archive (PC, CD)a more permanent archive (PC, CD)Finding software to replay the files you’ve Finding software to replay the files you’ve
acquiredacquired
Copyright Tasko & Finan 2008Copyright Tasko & Finan 2008
Free (yes, free) software for Free (yes, free) software for recording/analyzing high quality speech recording/analyzing high quality speech
signalssignalsSpeech ToolSpeech ToolSFSWin (UCL Phonetics Lab)SFSWin (UCL Phonetics Lab)AlvinAlvinWavesurferWavesurferPraatPraatAudacityAudacity
Copyright Tasko & Finan 2008Copyright Tasko & Finan 2008
Issues with PC recordingIssues with PC recording
Not all PC sound cards are identicalNot all PC sound cards are identicalVast majority work perfectly wellVast majority work perfectly wellOccasional problems includeOccasional problems include
Noise or staticNoise or staticShifts in recording baseline (does not affect Shifts in recording baseline (does not affect
how it sound)how it sound)