What are some of the functions of sound? Well one important reason is that we can't see everything. We need sound to alert us to certain stimuli. What are two possible definitions of sound? There is a physical definition and a perceptual definition. The physical definition is pressure that changes in the air or another medium. The perceptual definition is the experience we have when we hear.
SOUND WAVES
Objects make sound by moving back and forth rapidly through a medium. There is a difference between water and air waves. Water waves are transverse moving up and down, but sound waves move side to side.
Pure Tone
Pure tone is just a sine wave of a certain frequency. It is the simples form of a sound wave and all other sound waves are composed of pure tones.
Natural Sounds
These are relatively simple sounds, such as those mad by musical instruments, and are made up of many pure tones. Complex sounds have every at a broad range of frequencies and the relative energy at the different frequencies determine the pitch.
AMPLITUDE AND FREQUENCY
AMPLITUDE AND LOUDNESS: PHYSICAL VS PERCEPTUAL
The larger the amplitude is the larger our perception of that sound will be. The amplitude of sound waves is the difference in the pressure between these things. High pressure differences means that it has a high amplitude. This pressure is typically measured in micropascals but perception is typically measured in Decibels (dB).
Decibels
The log nature of the decibel scale compensates for the response compression of the auditory system. So what is the response compression? The idea is that you are more sensitive at the lower end but the louder the sound gets the harder it is to differentiate between differing sounds. This is a non linear relationship. So for example, if you increase the amplitude by 10 the perception in dB increases by 20, then amplitude going from 10 to 100 the dB goes only from 20 to 40, then the amplitude going from 100 to 1000 the dB only go from 40 to 60, and so on. If I were to say that something is twice as loud usually this speak is referring to dB and not amplitude.
FRQUENCY
Frequency is the number of amplitude cycles per second and is measured in Hertz. The higher we perceive frequency the higher the pitch. Tone height is the increase in pitch that happens when frequency is changed.
Musical Scales and Frequency
The letters in the musical scale repeats and notes with the same letter name have the same tone chroma, they sound similar. So if you were to take a low A, 27.5 Hz, then each octave higher would be double of the A one octave lower.
THE AUDIBILITY CURVE
The idea is that the audibility curve tells us the relationship between frequency and your perceived loudness (dB). Our hearing range is 20 to 20,000 Hz with greatest sensitivity to 2,000 to 4,000 Hz. The audibility curve shows the threshold of hearing. For really low turns it takes much more amplitude for us to be able to hear it.
EQUAL LOUDNESS CURVES
This is where you take 2 tones played at the same frequency but one with double the dB of the other. then you change the frequency of one of these sound curves and ask how the dB changed compared to the unchanged frequency. The basic idea of this curve is that low pitches have to be louder.
SOUND WAVES
Objects make sound by moving back and forth rapidly through a medium. There is a difference between water and air waves. Water waves are transverse moving up and down, but sound waves move side to side.
Pure Tone
Pure tone is just a sine wave of a certain frequency. It is the simples form of a sound wave and all other sound waves are composed of pure tones.
Natural Sounds
These are relatively simple sounds, such as those mad by musical instruments, and are made up of many pure tones. Complex sounds have every at a broad range of frequencies and the relative energy at the different frequencies determine the pitch.
AMPLITUDE AND FREQUENCY
AMPLITUDE AND LOUDNESS: PHYSICAL VS PERCEPTUAL
The larger the amplitude is the larger our perception of that sound will be. The amplitude of sound waves is the difference in the pressure between these things. High pressure differences means that it has a high amplitude. This pressure is typically measured in micropascals but perception is typically measured in Decibels (dB).
Decibels
The log nature of the decibel scale compensates for the response compression of the auditory system. So what is the response compression? The idea is that you are more sensitive at the lower end but the louder the sound gets the harder it is to differentiate between differing sounds. This is a non linear relationship. So for example, if you increase the amplitude by 10 the perception in dB increases by 20, then amplitude going from 10 to 100 the dB goes only from 20 to 40, then the amplitude going from 100 to 1000 the dB only go from 40 to 60, and so on. If I were to say that something is twice as loud usually this speak is referring to dB and not amplitude.
FRQUENCY
Frequency is the number of amplitude cycles per second and is measured in Hertz. The higher we perceive frequency the higher the pitch. Tone height is the increase in pitch that happens when frequency is changed.
Musical Scales and Frequency
The letters in the musical scale repeats and notes with the same letter name have the same tone chroma, they sound similar. So if you were to take a low A, 27.5 Hz, then each octave higher would be double of the A one octave lower.
THE AUDIBILITY CURVE
The idea is that the audibility curve tells us the relationship between frequency and your perceived loudness (dB). Our hearing range is 20 to 20,000 Hz with greatest sensitivity to 2,000 to 4,000 Hz. The audibility curve shows the threshold of hearing. For really low turns it takes much more amplitude for us to be able to hear it.
EQUAL LOUDNESS CURVES
This is where you take 2 tones played at the same frequency but one with double the dB of the other. then you change the frequency of one of these sound curves and ask how the dB changed compared to the unchanged frequency. The basic idea of this curve is that low pitches have to be louder.
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