# Shared Flashcard Set

## Details

Hearing Science Test 1
Sound Waves, Logs, Exponents, Decibels, Sinusoids
58
Audiology
09/21/2015

Term
 What are the 2 properties a source must have to vibrate?
Definition
 mass (m) and elasticity (E)
Term
 What is mass?
Definition
 – The amount of matter present – Applies to gases (**AIR**), liquids, & solids – Air has both mass and weight
Term
 What is weight?
Definition
 Weight is a gravitational force Weight is a force
Term
 What is Elascticity?
Definition
 - Property that enables recovery from distortion of shape or volume (e.g. pinching skin)   – Air – the tendency of air volume to return to its former volume after compression (e.g., syringe)
Term
 Newton's Interial Law
Definition
 All bodies remain at rest or in a state of uniform motion unless another force acts in opposition   • Magnitude of inertia is directly proportional to the mass
Term
 Newton's Third Law
Definition
 With every force there must be an equal and opposite reaction force – Hammer & nail, bat & ball – Force cannot exist by itself
Term
 Vibration
Definition
 – elasticity is the reaction force to inertia – Vibration sustained by opposing forces (i.e., inertia) – For a period of time vibration continues without reapplication of external force
Term
 Movement of Air Mass
Definition
 • When the density of air increases we call that compression   • When the density of air decreases we call that rarefaction   • So, when a sound travels through air there will be alternate regions of compression and rarefaction   • The medium of air is not displaced over a great distance   • The wave of disturbance moves through the medium
Term
 Sound
Definition
 characterized by propagation of density changes through an elastic medium   • When we talk about sound we need to consider specific physical quantities such as: – Mass – Density – Force – Pressure – Displacement
Term
 Systems of Measure
Definition
 • There are three basic physical quantities – Length – Mass – Time   • All other physical quantities are derived – Displacement – Velocity – Acceleration – Force – Pressure   • Metric: MKS & cgs   – MKS • Length (m) • Mass (kg) • Time (s)   – cgs • Length (cm) • Mass (g) • Time (s)   • English: fps – Length (ft) – Mass (lb) – Time (s)
Term
 Length
Definition
 • A measure of distance: the amount of spatial separation between two points   – How many times a unit (m, cm, ft) is contained in a given distance
Term
 Mass
Definition
 • The quantity of matter present • Defines the magnitude of inertia • Inertia is proportional to mass • MKS – kilogram (kg) • cgs – gram (g) • fps – pound (lb) • The quantity of mass defines the amount of inertia
Term
 Time (t)
Definition
 • A quantity expressed in seconds (s), minutes (min), hours (hrs), etc.   • Units of measure: – MKS – second (s) – cgs – gram (s) – fps – pound (s)
Term
 Displacement (x)
Definition
 • A change in position • A vector quantity: incorporates both magnitude and direction
Term
 Velocity (c)
Definition
 – The amount of displacement per unit time, OR – The time‐rate of displacement – Also a vector quantity – Average velocity • c = derived displacement (x)/time (t)   • Speed is a scalar quantity (i.e., only magnitude) • s = d/t   Displacement per unit time • MKS – m/s • cgs – cm/s • fps – ft/s, mph, etc.
Term
 Acceleration (a)
Definition
 • The time‐rate change in velocity • A vector quantity • Positive vs. negative acceleration (deceleration) • a = Δc/t = (c2‐c1)/t
Term
 Force (F)
Definition
 • A push or a pull • The product of mass (m) and acceleration (a) • F = ma • Object has mass (inertia), which opposes change in motion: force is applied to overcome inertia   • Consequences of force – Distortion of matter, and/or – Acceleration of matter   Units of Measure: • MKS – newton (N) – Force required to accelerate a mass of 1 kg from c = 0 m/s to c = 1 m/s in 1 s   • cgs – dyne – Force required to accelerate mass of 1 g from c = 0 cm/s to c = 1 cm/s in 1 s • 1 N = 100,000 dynes
Term
 Pressure
Definition
 Pressure is a force exerted over an hour on the surface of an object   Pressure decreases as the area over which a force is applied increases. • Force per unit area • p = F/A • p = 1 N/ 100 m2 = 0.01 N/m2 Units of Measure • 1 N = 100,000 dynes • 1m = 100 cm • Thus, 1 N/m2 = 100,000 dynes/m2 (m X m) 1 N/m2 = 100,000 dynes/10,000 cm2 (100 cm X 100 cm) • Thus, 1 N/m2 = 10 dynes/cm2   The Pascal (Pa) • 1 Pascal (Pa) = 1 N/m2 or 10 dynes/cm2
Term
 Acoustic Power
Definition
 • Sound energy is transferred through a medium at some rate   • POWER: the rate at which energy is transferred; Energy transferred per unit time   • ENERGY: the capacity to do work, whereas POWER is the rate at which energy is expressed The WATT – 1 WATT = 1 joule/s (MKS):
Term
 Sound Intensity
Definition
 • Intensity: Energy per second per square meter • Units of Measure – Intensity: watt/m2   • Absolute: The intensity is 3.15 X10‐2 watt/m2 • Relative: Level = Ix/Ir • For each value of Ix, the ratio Ix/Ir (the level) depends on the value of Ir
Term
 The Bel
Definition
Term
 10-fold change in Ix? 10-10 to 10-9
Definition
 dB changes by 10
Term
 2-fold change in Ix? 2x10-6 to 4x10-6
Definition
 dB changes by 3
Term
 Intensity Level (dB IL)
Definition
 the reference intensity must always be specified Ir = 10-12 watts/m2
Term
 Four Scales of Measurement
Definition
 • Nominal • Ordinal • Interval • Ratio
Term
 Nominal Scale
Definition
 • Objects are the same or different • The letter A is different from the letter B • The numeral (or a symbol that labels something) 1 is different from the numeral 0
Term
 Ordinal Scale
Definition
 • Two things are the same or different and, • One object has more or less of some quantity than another • Letters are not numbers: cannot be added • Numerals are not numbers either: can’t be added • E.g., doctor using a scale of 0‐10 to indicate degree of improvement in some condition(0 no improvement) and (10 disappearance of the condition)
Term
 Interval Scale
Definition
 • Size of the interval between adjacent numbers is known and is constant • The size of the interval is called the BASE • Successive units are formed by adding (or subtracting) base to each number • Because the base is known we can say that one object is a certain number of intervals more or less than another
Term
 Ratio Scale
Definition
 • One unit on the scale is so many times greater or less than another • Successive units are formed by multiplying (or dividing) each number by the BASE • Successive units differ by a constant ratio, which is the BASE • The numbers on the scale differ by a constant ratio, and • They can be expressed as the base, 2 in the previous example, raised to progressively higher powers
Term
 Laws of Exponents
Definition
 • 1. Law 1: (Xa)(Xb) = Xa+b • 2. Law 2: Xa/Xb= Xa-b • 3. Law 3: (Xa)b= Xab
Term
 Laws of Logarithms
Definition
 • 1. Law 1: Log ab = Log a + Log b • 2. Law 2: Log a/b = Log a – Log b • 3. Law 3: Log ab = b Log a • 4. Law 4: Log 1/a = ‐ Log a
Term
 Sound Pressure
Definition
 • Pressure is force/unit area • Unit of measure (MKS):  N/m2  Pa, where 1 Pa = 1 N/m2   μPa, where 1 μPa = 1 μN/m2   To derive an appropriate equation, we consider intensity and pressure in relation to impedance of the medium.   • I is proportional p2 • OR, p √I (the square root of I)   • dB IL: Ir = 10-12 watt/m2 • An intensity of 10-12 watt/m2 creates a pressure in air of 20 (2 X 101)µPa • Therefore, for dB SPL, the reference pressure, pr, is 20 µPa • pr is 2 X 101µPa   dB SPL = 20 log (px/pr)
Term
 2-fold change in px? 2x105 to 4x105
Definition
 dB increases by 6dB
Term
 10-fold change in px?
Definition
 dB increases by 10dB
Term
 Combining Sound Intensities from Independent Sources Equal Source Intensities
Definition
 • dBN = dBi + 10 log10N, i = dB SPL (or dB IL) from one source N = # of sources combined
Term
 Combining Sound Intensities from Independent Sources Unequal Source Intensities
Definition
 • Three steps in solution 1. Calculate intensity from each source 2. Add intensities (carefully) 3. Calculate decibels   • One source = 80 dB SPL, and a second source = 83 dB SPL • dB = 80 Ix = 1 X 10-4 • dB = 83 Ix = 2 X 10-4 • Sum of Ix = 3 X 10-4   • dB = 10 log (3 X 10-4 /10-12) = 10 log (3 X 108) = 84.8 dB IL (dB SPL)
Term
 Transmission of Sound
Definition
Term
 Vibrations can be...
Definition
 • Periodic • Aperiodic
Term
 Sine Waves
Definition
 Building blocks of all sound
Term
 Characteristics of a Sine Wave
Definition
 • Frequency/Period   • Phase   • Amplitude • (wavelength)
Term
 Frequency
Definition
 – How quickly a sine wave  repeats itself – Number of cycles  completed in 1 sec – Unit: Hertz f = 1 / T (f = 1 / Pr)
Term
 Period (Pr, T)
Definition
 – How long it takes to complete 1 cycle. – Unit: sec, ms   T = 1 / f (Pr = 1 / f)
Term
 Period/Frequency Units
Definition
 • sec vs. ms       milli = 1/1000   1 ms = 0.001 sec   1 sec = 1000 ms   • milli vs. micro       milli = 1/1000   micro = 1/1,000,000   • Hz vs kHz       kilo = 1000 times   1000 Hz = 1 kHz 2 kHz = 2000 Hz
Term
 Wavelength (λ)
Definition
 • Distance traveled during one period  • Equation:  λ = s / f   s = speed of sound f = frequency   • Examples in air (s = 340 m/s) f = 1100 Hz • λ = 340/1100 = 0.3m   f = 550 Hz • λ = 340/550 = 0.6m
Term
 Amplitude
Definition
 • How big is the displacement, how far did the       vibrating object move? • Types of amplitude:       Peak Peak‐to‐Peak (2 x Peak)       RMS amplitude
Term
 Amplitude
Definition
 • How big is the displacement, how far did thevibrating object move?• Types of amplitude:PeakPeak‐to‐Peak (2 x Peak)RMS amplitude
Term
 RMS Amplitude
Definition
 • RMS = root‐mean‐square 1. square amplitudes 2. compute mean (average) 3. compute square root   • RMS = 0.707A • Peak Amplitude = 1.414RMS
Term
 Complex Stimuli
Definition
 • Composed of more than one sine wave • Harmonic complex – All sine waves are integer multiples of the lowest frequency – Terminology: • f0, f1, f2, f3, f4, etc. = harmonics   f0 and f1 are the same   sound composed of sine waves at the following frequencies: 125, 250, 375, 500, 625, 750, 875, 1000 Hz • Speech sounds may be harmonic complexes Example: Vowel sound might consist of f0 = 200 Hz and 40 harmonics.
Term
 Complex Stimuli: Transients
Definition
 – Sounds with very short duration – AKA click, tone burst, impulse – Examples: hand clap, gun shot
Term
 Complex Stimuli: Noise
Definition
 – Amplitude varies randomly over time – Example: White noise
Term
 Time Domain of Stimuli
Definition
 – Amplitude variations as a function of time – Temporal waveform - time waveform - x-axis is time
Term
 Frequency Domain of Stimuli
Definition
 – Amplitude variations as a function of frequency – Spectral representation/amplitude spectra/power spectra - x-axis is frequency
Term
 Fourier Analysis
Definition
 takes a complex waveform and figures out all the individual sine waves that make it up
Term
 Noise
Definition
 • Broadband or white noise – All frequencies present – Amplitudes distributed according to a Gaussian (standard bell curve) distribution – Phase relationship of the components is random – White noise = Gaussian noise - white noise is aperiodic
Term
 Narrowband Noise
Definition
 • Noise that has more limited frequency content than white noise • How do you create narrowband noise? – Pass white noise through a filter   Characterizing Frequencies: - what frequencies "pass - cutoff frequency - rejecction rate
Term
 [image]
Definition
 Top: Low Pass, let low frequencies through  Top/Middle: High Pass, let high frequencies through Bottom/Middle: Band Pass Bottom: Band Reject
Term
 Overall Level/Total Power Measure for Noise
Definition
 • The sum of all the sinusoids present in the       noise
Term
 Spectrum Level (N0) Measure for Noise
Definition
 • Energy in any single component of noise must be less than the total power • Spectrum level is the average power in 1‐Hz band of the noise • N0 = spectrum level • OAL = overall level of noise (total power) in dB • BW = bandwidth of noise in Hz • N0 = OAL – 10 log BW
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