Basic Acoustic and Terminology Flashcards
Define Sound.
Vibratory energy transmitted by pressure waves in air or other media that is the objective cause of the sensation of hearing.
In simple terms sound is _________.
Vibrations.
What do all sources of sound involve?
They involve moving or vibrating structures.
Energy is converted from ______ energy to ______ energy.
mechanical
sound
What is the fancy name for sound travelling?
Sound transmission.
As the sound source vibrates- what happens?
Air molecules around the source vibrate and pass on the vibrations to the adjacent molecules.
Explain sound transmission.
Waves of high pressure (compression) and waves of low pressure (rarefaction) travel through the air.
As sound travels outwards from the source the same amount of sound energy has to cover a bigger space- what happens to the sound?
It becomes quieter.
As the sound wave moves out from its source, energy is _____________ in the form of heat.
dissipated
The energy of the sound wave _______ as the distance from the sound increases.
Decreases
Does sound travel faster in water or faster in air?
In water.
A ______ cannot pass sound energy.
vacuum.
What does a tuning fork produce?
The most basic sound- a sinusoidal wave.
The most basic sound is known as a _______ ________.
sinusoidal wave.
What is a sine wave made up of?
One frequency of vibration of the air molecules.
A tuning fork produces a clean and sharp sound known as a ___________ tone.
Pure
Name the 3 characteristics of a sinusoid.
Amplitude
Frequency
Phase
Name this-
A measure of the magnitude of pressure changes in the medium concerned.
Amplitude.
Amplitude means _______.
Loudness.
What scale do we use to measure sound?
Decibels (dB)
What is an advantage of dB?
It is similar to the human subjective perception of loudness.
What is the human hearing range?
0-140 dB
Name this-
The number of wave cycles in one second.
Frequency
What is frequency?
The Pitch.
As the number of cycles per second increases the ____ of the sound ____________.
Pitch, Increases.
Name sound that’s too low to hear.
Infrasound.
Name sound that’s too high to hear.
Ultrasound.
What can be found in musical instruments and human voice?
Harmonics.
What is harmonics?
A series of sound evenly spaced out.
The tone with the lowest frequency is called the _______________ _______________.
Fundamental Frequency.
The higher notes on top of the fundamental frequency are called what?
Overtones.
Overtone with frequency that’s a multiple of the fundamental frequency is called ___________.
Harmonics.
The normal human ear is able to detect, identify and _______ amongst many sounds.
Differentiate.
A normal hearing listener can detect very small differences in __________ and ______________.
Amplitude (loudness)
Frequency (pitch)
What is used to asses patients hearing thresholds?
Pure Tone Audiometry.
What is a hearing threshold?
The quietest sound a person can hear.
Name the 2 types of Pure Tone Audiometry that can be performed.
Air Conduction
Bone Conduction
Air conduction and Bone conduction covers the ______ range.
speech
The lower the points on the audiogram, the ________ the hearing.
worse
What is used to present the tones during pure tone audiometry?
An audiometer.
All speech sounds are marked on the audiogram- what do we call this?
The speech banana.
If somebody has mild hearing loss they will find what sounds difficult to differentiate between?
Fricatives
some nasals
If someone can’t distinguish between [p] and [b] they are likely to have ______ hearing loss.
moderate.
name this:
A description of where, at a point in time, the sound wave is during its repeating cycle.
Phase.
Two waveforms can have the same frequency and amplitude, but a different ________.
Phase.
If 2 sin waves of the SAME frequency and SAME phase from different sources coincide what happens?
The regions of either BOTH POSITIVE PRESSURE or BOTH NEGATIVE PRESSURE combine.
This is called constructive interference.
In constructive interference what happens to the sound?
It doubles the amplitude aka. its twice as loud.
Describe Destructive Interference.
If 2 signals are out 180 degrees of phase, the positive and negative portions cancel each other out - there is no sound.
What interference creates no sound as the waves cancel each other out?
Destructive interference.
In interference if signals aren’t on the same frequency what sound is created?
A pulsing sound called the beat phenomenon.
What is responsible for dead spots in an auditorium?
Destructive interference.
What is responsible for live spots in an auditorium?
Constructive interference.
Sound reflection, sound absorption, reverberation and attenuation all come under the heading of _____ ________.
room acoustics.
What 3 things happen when a sound meets a surface?
Some sound energy is absorbed
Some is reflected
Some is lost as heat.
What does an anechoic chamber do?
It reduces the reflection of sound, it absorbs all echoes.
Name this:
The sound remaining after the sound source has stopped.
Reverberation.
The time taken for the sound intensity to drop by 60dB from it’s original level is known as it’s ___________ time.
Reverberation.
A cathedral has a ____ reverberation time.
Long.
Precedence effect-
Direct sound always arrives ______ and always from the correct direction.
But there are lots and lots of ______ from all the surfaces and objects in the room (i.e. reverberation).
First
reflections
What is attenuation?
The stopping os sound by enclosure or shielding.
How do we measure sound energy?
Sound meter.
What piece of equipment measures the noise level of a particular environment to check if it’s safe?
Dosimeter
What is the dummy that measure what a human would hear called?
Free Field Calibration
