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CSD 2230 INTRODUCTION TO HUMAN COMMUNICATION DISORDERSPowerPoint AccessThe Perception of SoundSlide 4Overview of PerceptionQuestions to AskSlide 7Hearing AcuityNormal Auditory SensitivityAuditory AreaThe Normal Auditory AreaIntensities of Common SoundsThresholdsDifferential Sensitivity for IntensityDifferential Sensitivity for FrequencyCharacteristics of Normal Sound Perception and SpeechAcoustic Cues of SpeechCategorical PerceptionSlide 19Sounds Perceived Non-CategoricallySounds Perceived CategoricallyPerception of Some Voiced vs. Unvoiced ConsonantsVoice Onset TimeVOT Waveform for a Voiceless StopVOT Waveform for a Voiced StopCategorical Perception of VOTNeat….Huh???Infant StudiesSlide 29Nonbehavioral Measures of Hearing AcuityBehavioral Responses of Infants and NewbornsReflexive Behaviors to Loud SoundsAttentive Behaviors in Newborns and InfantsSlide 34Behavioral Responses of InfantsVisual Reinforcement AudiometrySlide 37Infant Speech PerceptionSlide 39PowerPoint PresentationSlide 41Three Important Conclusions Regarding Speech Perception DevelopmentOlder AdultsHearing Loss and AgingAudiologic Characteristics Associated with AgingChanges in Detection as a Function of Age and GenderSlide 47Slide 48Slide 49CSD 2230INTRODUCTION TO HUMAN COMMUNICATION DISORDERSNormal Sound Perception, Speech Perception, and Auditory Characteristics at the Boundaries of the LifespanPowerPoint AccessYou may access this presentation through my website: click on the CSD 2230 link on my home page.The Perception of SoundWhat do we hear when we listen to a sound??The Perception of SoundPsychoacoustics is a branch of experimental psychology interested in these questionsOverview of PerceptionnAlthough the physical characteristics used to measure sounds are objective, how we experience sounds is subjectiveObjective Characteristics•Intensity •Frequency•DurationSubjective CharacteristicsPitchLoudnessQuestions to AskWhat are the limits of our ability to sense sound? How do our subjective impressions of sounds change as we change the physical dimensions of sound?Overview of PerceptionHow we experience sounds is subjectiveListeners are variable in their responsesHearing AcuityWhat are our limits in detecting sounds?Audibility and detectabilityFrequency and intensity restrictionsNormal Auditory SensitivityNormal hearing listeners are capable of detecting sounds within a range of 1 Hz up to about 20,000 HzSensitivity is NOT equal across this rangeBest sensitivity is between 1000-5000 HzAs the frequency of the sound moves above or below this range, sensitivity gets progressively worseAuditory AreanThe useful range of hearing for any individual is taken to be the area between the person’s absolute threshold and the threshold of feelingThe Normal Auditory AreaUseful frequency range is between 20 and 20,000 HzDynamic range is widest between 1000 and 5000 HzWidest range is 120 dBIntensities of Common SoundsThresholdsAbsolute sensitivity--the minimum intensity at which a listener can distinguish sound from silenceüDetectionDifferential sensitivity--the smallest change in a stimulus a listener is just able to detectnDiscriminationDifferential Sensitivity for IntensityIntensity discrimination depends on whether sounds are close to absolute threshold or far from thresholdIn general, for a wide range of stimulus intensities and frequencies, our discrimination ability for intensity is 2 dB or lessDifferential Sensitivity for FrequencyOur resolving power for frequency isn’t as good as for intensityFrequency discrimination depends on the general frequency range of the two soundsCharacteristics of Normal Sound Perception and SpeechAcoustic Cues of Speech1. Frequency2. Intensity 3. Temporal CharacteristicsCategorical PerceptionRepresents an important way in which speech is processed differently by humans than other soundsIllustrated by comparing our ability to discriminate and identify certain kinds of soundsCategorical PerceptionDiscrimination is the ability to tell if two sounds are the same or differentIdentification is the ability to label a soundSounds Perceived Non-CategoricallynMusicWe can discriminate more than 1000 different notes (pitches) but most of us can only identify about 7.Big difference between what we can discriminate and what we can identifySounds Perceived CategoricallynSpeechnWe can discriminate the same number of speech sounds (phoneme) that we can identifyPerception of Some Voiced vs. Unvoiced ConsonantsDiscriminating /p/ from /b/, /t/ from /d/, or /k/ from /g/These are English consonants that are formed the same way (manner of articulation) and formed in the same area (place of articulation) of the vocal tract but differ in terms of whether the vocal folds are vibrating during production (voicing)Voice Onset TimeThe difference in these phoneme pairs is in the timing of when the larynx starts to vibrate during the production of the consonantvoice onset time (VOT)Voiced stops have a relatively short VOTVoiceless stops have a longer VOTVOT Waveform for a Voiceless StopnVOT measure for /p/. LO represents the release of the burst (stop). RO is placed at the highest point of the first cycle of vocal fold vibration. Notice the relatively long time interval between these two points.VOT Waveform for a Voiced StopnVOT measure for /b/. LO represents the release of the burst (stop). RO is placed at the highest point of the first cycle of vocal fold vibration. Notice the relatively short time interval between these two points.Categorical Perception of VOTnIdentification functions of a single listener for VOT continuum from /d/ to /t/ in 11 ms steps.Neat….Huh???The big question is:Are we born with this ability to perceive speech categorically? OrDo we eventually learn to perceive speech categorically?Infant StudiesnBefore birthWhen do we first hear?What do we first hear?Infant StudiesnAcuity after birthHow do we measure this?Why is it important to know ASAP??Nonbehavioral Measures of Hearing AcuityAuditory Brainstem Response (ABR)Otoacoustic Emissions (OAEs)Behavioral Responses of Infants and NewbornsnThe auditory responses of infants can be described in terms of reflexive behaviors and attentive behaviorsReflexive Behaviors to Loud SoundsnReflexes observed when loud sounds are presented to an infant:nThe startle responsenThe auropalpebral responseAttentive Behaviors

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