UNIT VI DSP in Speech Processing & Image Processing Audio Processing: Human Hearing, Timbre, Sound Quality Versus Data rate, High Fidelity Audio, Companding, Speech Synthesis and Recognition, Non Linear Audio Processing Image Foundation and Display: Digital Image Structure, Cameras and Eyes, Television Video Signals, Other Image Acquisition and display, Brightness and Contrast Adjustments, Gray Scale Transforms

Audio Processing

Structure of the human ear Human hearing Structure of the human ear Phys1061, S.Boyd

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Important parts of the ear Human hearing Important parts of the ear Outer Ear: Auditory canal Ear drum Middle ear: Ossicles: hammer (malleus), anvil (incus), stirrup (stapes) Inner Ear Cochlea Auditory nerve Phys1061, S.Boyd

Frequency response localized in Cochlea Neuronal Decoding of Sound (Schematic) Low Frequency High Frequency Frequency response localized in Cochlea

Mechanism of signal transport Human hearing Mechanism of signal transport Hall, Musical Acoustics, 3rd Ed. Phys1061, S.Boyd

Copy out these notes Pinna = outer portion of ear used to collect sound waves Auditory Canal = tube that sound travels down Ear Drum = membrane that sends sound waves to hammer Hammer = first of 3 bones. It vibrates, striking the anvil to carry on the sound Anvil = gets hit by the hammer, striking the Stirrup Stirrup = vibrates against OVAL WINDOW, carrying on sound Cochlea = a spiral full of sensory “hairs,” which when bent, send an electrical signal to the AUDITORY NERVE Auditory Nerve = carries all signals for sound to brain SemiCircular Canals = full of gel-like material. Indicates if you are right side up or upside down. (Balance)

Structure of the Ear

designed to gather and collect sound into the ear canal Outer Ear = Pinna designed to gather and collect sound into the ear canal

Middle Ear – the Auditory Canal Channels the sound toward the EAR DRUM

Middle Ear – the Ear Drum is actually called the “TYMPANIC MEMBRANE” Sound waves = vibrations HAMMER hits ANVIL moving the STIRRUP!

What Happens Next? Sound waves travel into the SPIRALLED COCHLEA Tiny hairs in the COCHLEA move to the beat, and send impulses along nerve fibers All nerve fibres link to the AUDITORY NERVE, to the brain.

Inside the COCHLEA! Eustacian Tube

Detectable Sound Levels – What can the Machinery Pick UP?

What Frequencies can we Hear? 2 000 - 20 000 Hz 100 000 – 140 000 Hz

Detectable Sound Levels – What can be Heard?

Sound Wave Production Levels of Intensity Soft (Low) Harsh(High)

Defeating Deafness – Cochlear Implants The implant generates electric signals as the sound bounces off detector Vibrations = electricity Electricity stimulates the AUDITORY NERVE directly

Protect your Hearing! Ear plugs Ear – muffs Keep the volume down

Spidey knows the Value of Protecting Your Hearing!

Copy out these notes Pinna = outer portion of ear used to collect sound waves Auditory Canal = tube that sound travels down Ear Drum = membrane that sends sound waves to hammer Hammer = first of 3 bones. It vibrates, striking the anvil to carry on the sound Anvil = gets hit by the hammer, striking the Stirrup Stirrup = vibrates against OVAL WINDOW, carrying on sound Cochlea = a spiral full of sensory “hairs,” which when bent, send an electrical signal to the AUDITORY NERVE Auditory Nerve = carries all signals for sound to brain SemiCircular Canals = full of gel-like material. Indicates if you are right side up or upside down. (Balance)

Inverse Square Law, Sound

Units of sound intensity Units of sound intensity. Sound intensity is expressed as power per unit area (such as watts/cm2), or more commonly on a logarithmic scale called decibels SPL(Sound Pressure Level). As this table shows, human hearing is the most sensitive between 1 kHz and 4 kHz.

Decibel levels of some common sounds Sound Source Sound Pressure Level (dB) threshold of excellent youthful hearing normal breathing, threshold of good hearing 10 soft whisper 30 mosquito buzzing 40 average townhouse, rainfall 50 ordinary conversation 60 busy street 70 power mower, car horn, ff orchestra 100 air hammer at 1m, threshold of pain 120 rock concert 130 jet engine at 30m 150 rocket engine at 30m 180 More decibel levels here: http://www.lhh.org/noise/decibel.htm

Audio data rate vs. sound quality

Laser Wavelength

The Piano keyboard The keyboard of the piano is a logarithmic frequency scale, with the fundamental frequency doubling after every seven white keys. These white keys are the notes: A, B, C, D, E, F and G.

Pregroove on (Re)Writable Disks empty track land mark (data) laser beam written wobbled pregroove (Re)Writable Disk CD stores about 1 bit per (μm)2, corresponding to 1 million bits per (mm)2, and 15 billion bits per disk.

Timbre Loudness: sound wave intensity Pitch: fundamental component in the sound Timbre : harmonic content of the signal

High Fidelity Audio Compact disc surface

Playback-CD During playback, an optical sensor detects if the surface is reflective or nonreflective, generating the corresponding binary information. Binary one must be part of a group of 3 to 13 ones Two-level Reed- Solomon coding: combining the left and right stereo channels along with data for error detection and correction

-Cont Compact disc playback block diagram EFM: Eight-to-Fourteen Modulation

Speech Synthesis and Recognition Human speech model

Nonlinear Audio Processing Homomorphic separation of multiplied signals

Homomorphic separation of convolved signals