Presentation on theme: "Overview of Human-Machine Systems The Human-Machine Interface Cognitive Functions Motor Functions: Human Output Sensory Systems: Human Input Controls:"— Presentation transcript:
Overview of Human-Machine Systems The Human-Machine Interface Cognitive Functions Motor Functions: Human Output Sensory Systems: Human Input Controls: Machine Input Displays: Machine Output Mechanisms of Machine: Performs Task and Determines State Feedback within Machine Muscular Feedback
Physical Stimulus Accessory Structures Receptors (Transduction) Neural Processing Perception/ Cognition Behavior Light, Sound, Pressure, Chemical substances, Temperature, etc. Eye (cornea, lens …) Ear (pinna, ossicles…) Skin, Tongue (tastebuds), …. Rods, Cones, Hair cells Chemo- receptors Pacinian corpuscles ….. Locally and centrally so many steps Our experience The output of all this
General Characteristics of Sensory Systems StimulusReceptorNeural Relay Cortex In Vision LightRods/ConesLGN of ThalamusStriate In Audition SoundHair CellsMGN of ThalamusSup. Temp. G. Other Generalities Always more than one pathway in brain Always more than one brain target Ultimately sensory information is combined
The Physical Stimulus for Audition java illustration java illustration The sound wave is periodic changes in pressure Frequency = cycles/second = Hertz, Hz. Frequency = 1/Wavelength Wavelength Amplitude or Intensity
The Physical Stimulus for Audition - 2 Amplitude is the difference in air pressure between the compression and rarefaction. The measure of sound amplitude is the relative measure called decibel or dB. Where P = air pressure; P 2 = power dB SPL, P 2 =0.0002 dynes/cm 2 which is near the absolute threshold for hearing.
The Physical Stimulus for Audition - 3 Resonance All physical mater will most easily vibrate at certain frequencies. This is true of our ear. Thus some frequencies will more easily enter our ear It helps us determine the frequencies of incoming sounds as we shall see. The physical dimensions are related to but not the same as the psychological dimensions: frequency <> pitch amplitude <> loudness
Anatomy and Physiology of the Ear Three Major Divisions Outer Ear receives sound directs it to the rest of the ear. Pinna - directs sound energy to middle ear and helps perception of the direction. External Auditory Meatus or Canal - 2.5 to 3 cm long, 7 mm wide Resonates at about 2-4K Hz. Tympanic Membrane
Anatomy and Physiology of the Ear - 2Ear Middle Ear transmits sound information to inner ear. Ossicles transmit and amplify sound energy. Malleus - Hammer Incus - anvil Stapes - stirrup Eustachian Tube Inner Ear is where transduction of sound information occurs. Cochlea (snail) with the Oval Window Round Window
The Cochlea and Sound Transduction The Cochlea - Latin for snail which is what it looks like Basilar membrane runs most of the length of the cochlea dividing in the top and bottom. The base is right below the oval window where the sound energy enters The apex is at the other end. Hair Cells are the receptors and run the length of the Basilar Membrane in two sets inner 1 row ~ 3500 outer 3 rows ~20000 Tectorial Membrane - across top of Hair Cells
The Cochlea and Sound Transduction - 2 Auditory Transduction Transduction is the conversion of energy from one form to another, e.g., sound pressure to neural impulses The Traveling Wave.Traveling Wave Wave set up by action of stapes on oval window Point of Maximal Displacement depends upon the frequency of the tone. High Frequencies near the base. Low frequencies near the apex. The Shearing ForceShearing Force The traveling wave bends the basilar membrane This bends the hair cells.
Loudness The experience of sound most closely related to amplitude or intensity. Examples of sounds at different d SPL levels for comparison. Rustling Leaves=~20 d Average Speaking Voice=~60 d Heavy Traffic=~80 d Rock Band=~120 d Pain/Damage Threshold=~130 to 140 d Loudness differs in many ways from intensity. The threshold depends upon intensity and frequency. Intensity doubles every 6 dB; loudness doubles every ~8 dB.
Pitch The dimension of sound that most closely relates to frequency. The higher the frequency the higher the pitch. Discrimination between two pitches depends on the frequency of the lower pitch: Weber Fraction: (f 1 - f 2 )/f 2 = 0.004 e.g. (251-250) / 250 = 0.004 (1004-1000) / 1000 =0.004 Pitch is not the same as frequency Pitch will change as intensity is increase and frequency is kept constant.
The Interdependence of Loudness and Pitch First studied by Fletcher and Munson (1933). Called Fletcher-Munson Curves or Equal Loudness Contours. Method: Subjects adjusted tone of different frequencies to match loudness of 1000 Hz tone the intensity of 1000 Hz tone was varied over trials. Thus, all tones that match a 1K Hz tone of a given intensity should all be equally loud and connecting those on a graph of intensity by frequency should give an equal loudness contour.
The Interdependence of Loudness and Pitch - 2 As intensity of the 1K Hz tone increase, the contours get flatter. Relates to the Loudness button on your stereo. This relationship again illustrates the difference between physical dimensions and psychological experience.
Application to Human Factors Sound Button on Stereo Most recording are at region where loudness if fairly constant across frequency. We may play at a lot lower level where loudness does depend on frequency Alters what we hear because we lose sensitivity to low and high frequencies faster than middle frequencies. Sound button compensates for this by boosting high and low frequencies.
Fourier Analysis A mathematical procedure to break down complex waveforms in to simple components, usually sinewaves. The ear does something like this.
Fourier Analysis - 2 Let us use this stimulus as our complex wave. It is called a square wave.
How Fourier Analysis Works - Briefly The Frequency Domain Frequency of Sinewave along the x-axis Amplitude of Sinewave along the y-axis
How Fourier Analysis Works - Briefly 2 Visual Illustration Auditory online illustration
Effects of Multiple Tones Beats Perception of intensity changes from two nearby frequencies From constructive and destructive interference Frequency of beating is difference in frequency between the two tones, e.g. 101- 100 = 1 Hz beats
Effects of Multiple Tones - 2 Missing fundamental Fundamental is lowest pitch of a tone higher frequencies called harmonics or partials Perceive a same pitch even without fundamental Allows us to tell female vs. male voices on the telephone.
Masking DEFINITION: one tone is rendered less perceptible by another auditory stimulus. Tone Masking low tones will mask higher tones better. due to shape of traveling wave (skewed towards base, higher frequencies). Noise Masking Noise is sound energy that lacks coherence. Beyond a point adding more frequencies to the noise does not increase masking. Critical bands: region of basilar membrane where sound energy is summed together.
Application to Human Factors Consider Noisy Environments How keep all the sounds distinguishable? Consider sirens and other alerting sounds? Is simply loud enough or necessary?
The Perception of Auditory Direction Eyes can see only in one direction at a time. Ears are not so limited. Interaural Time of Arrival Difference/Phase Description - sound has to travel farther to ear on farther side of head This difference can be detected if as small as 0.1 msec. Works for clicks and tones with frequencies < 1000 Hz Precedence Effect - Tendency to suppress later arriving parts of a sound Precedence Effect
The Perception of Auditory Direction - 2 Interaural Intensity Differences Description - Head shadows sound so that farther ear will hear a slightly less intense sound. Just as we suppress later sounds, we suppress less intense sounds. Works best for relatively high frequencies. This ability to hear sounds from all directions is useful to design alerts.