Sound and Auditory Perception Flashcards
(12 cards)
How is sound created?
When objects are disturbed, the molecules that constitute the object vibrate. These vibrations emit at a particular range of frequencies. The exact range of frequencies differ depending on the object but these ranges are called “natural frequencies”.
What are resonance frequencies
Most sound that we hear is a mixture of many frequencies, the frequency out of that range which has the most amplitude is called the resonance frequency.
What are sinusoidal waves?
Sinusoidal is often used to refer to pure tones which is the sound of a single frequency and is a type of a waveform. Sinusoidal waves are smooth and repetitive (having consistent frequency) oscillations that resemble the structure of a sine wave.
We can hear a pure tone upon striking a tuning fork.
What is the Fourier’s Analysis?
According to the Fourier’s Analysis, any complex waveform can be represented as a combination of simpler waves with fixed frequencies.
That is, by adding up waves of different frequencies, we can create any wave form.
How do different gases change the pitch of sound ?
Different gases have different molecular masses, the different masses lead to a difference in the speed with which sound travels through those mediums. Mediums consisting of molecules with lighter molecular mass lead to sound travelling through it faster and hence the wavelength and the frequency of the wave changing. The pitch of sound is dependent on its frequency and since the frequency is different, the pitch of the sound changes.
In the case of helium, this means: because the speed of sound is faster compared to air, the wavelength of the sound produced by your vocal cords becomes shorter. This means that more waves are packed into the same amount of time, leading to a higher frequency, which is perceived as a higher pitch.
Sound under Water
Sound moves faster under water compared to in the air. Sound also travels faster in warmer water compared to colder.
Humpback Whale noises were very popular and some people found them soothing.
Echolocation
Bats have the ability to echolocate by emitting high frequency sound pulses through their mouth or nose and listening to the echo. Using this echo bats can tell shape, size and texture of the objects in its surrounding.
Spectrogram
This is a visual representation of the frequencies and their amplitudes as they vary over time.
They are 2D representations with a third dimension of colour. Time is on the X axis and frequency on the Y. The amplitude is depicted by the colour. Blues indicating low amplitude and reds indicating higher ones.
The Vocal Tract as an Instrument
Nasal Cavity: The nasal cavity is lined with mucous membranes and contains structures that play a vital role in filtering, humidifying, and warming inhaled air before it reaches the lungs. Additionally, it contributes to vocal resonance (making sound louder) and articulation (saying nasal sounds), particularly in the production of nasal consonant sounds.
Oral Cavity: This one helps in articulation (shaping the sound) of words and also acts as a resonating chamber, altering sound waves’ frequencies to produce varied tones. It amplifies sound by reinforcing and strengthening it, aiding in speech projection.
Pharynx: This also does the same function as the above two and affects the timbre and frequency of sound.
Larynx: The vocal cords (aka vocal folds) vibrate (come closer and move apart) when air passes through and hence create sound waves. We can also control the pitch of the sound based on the movement of the vocal cords.
In summary, the Nasal Cavity, Oral Cavity and the Pharynx all help amplify the sound created by the Larynx.
How do we hear sounds?
What is Acoustic Impedance?
Acoustic impedance is a measure of the ease with which a sound wave propagates through a particular medium.
Sound Through Different Mediums
Different mediums have different Acoustic Impedances (aka there is a Impedance Mismatch) so when sound moves from one medium to another, some of the waves pass through while others reflect back.
