| How does experience help segregation of sound sources? | You are more likely to be able to segregate two melodies if you have heard them before separately.
Same for noises. |
| What is the perceptual definition of sound? | Sound is the experience (e.g. sensation) we have when we hear. |
| What rate do pressure waves (i.e. sound waves) move through air and water? | Air - 340m/s
Water - 1500m/s |
| When does a pure tone occur? | When the change in air pressure occurs in a pattern of a sine wave. |
| What is the relationship between frequency and pitch? | Higher the frequency, the higher the pitch (for pure tones). |
| What is the unit of frequency? | 1 Hz (Hertz) = 1 oscillation per second. |
| What is the range of human tones? | 20Hz to 20,000Hz |
| What is the relationship between amplitude and sound? | Greater the amplitude, the louder a sound seems. |
| What is the unit of amplitude? | Decibels (dB)
1 dB = 20 * logarithm (p/p0)
where: p - pressure in mPa
p0 - reference pressure (usually 20mPa) |
| What is the significance of 200Hz? | Fundamental frequency, or first harmonic.
Wave repeats every 5ms. |
| What are the units of perceptual loudness (for pure tones)? | Phons |
| What is pitch determined by? | Frequency.
For a complex tone, it is usually determined by the fundamental frequency.
People usually describe pitch in terms of musical notes. |
| What do equivalent musical tones in different octaves have in common? | The same chroma. |
| How does tone height increase? | As notes move left to right on the piano keyboard. |
| What are the attributes of pitch? | Tone height
Chroma |
| What does the missing fundamental do? | Determines the pitch of the complex tone. |
| Why do different instruments sound different? | Because different instruments produce different amplitude, making the resultant waveforms different.
They have different timbres |
| What is the difference between period and aperiodic sounds? | Periodic sounds - repeating waveform.
Aperiodic sounds - waveforms which don't repeat. |
| What are the types of periodic sounds? | Simple - single sinewave.
Complex - multiple sinewaves (due to harmonics). |
| What are the types of aperiodic sounds? | Continuous - noise.
Transient - pulse. |
| What is auditory localisation? | Being able to determine the position of an event/object based on auditory information. |
| What is auditory localisation based on? | Binaural cues
Monoaural cues |
| What do binaural cues include? | Interaural time difference.
Interaural level difference. |
| What is interaural time difference? | When one ear hears a sound before the other. |
| What is interaural level difference? | For high frequency sounds, there can be a large interaural level difference between ears due to the sound shadow caused by your head.
For low frequency sounds, the interaural level difference is much less. |
| What is the cone of confusion? | When two points have the same interaural time difference and interaural level difference, therefore you cannot distinguish between the two points using only binaural cues. |
| What is the monaural cue for elevation? | Sound bounces off different parts of the pinna (outer ear) before entering the ear canal.
Sound acquires characteristic frequency notches that depend on its elevation, which can be used to determine the elevation of the sound source. |
| When do you hear an echo? | When the temporal separation between two sounds is more than about a 10th of a second.
If the temporal separation is 5-20ms, you will not hear the second sound. |
| What are the factors that determine the quality of the architectural acoustics? | Reverberation time.
Intimacy time.
Bass ratio.
Spaciousness factor. |
| What is reverberation time? | Time it takes for sounds to decrease by 60dB.
For a concert hall, it should be about 2s.
For an opera hall, around 1.5s. |
| What is intimacy time? | Temporal difference between when the direct sound arrives and the first indirect sound arrives.
Concert halls - intimacy time of about 20ms. |
| What is base ratio? | Measured for indirect sound.
Ratio of low frequencies to middle frequencies for the indirect sound.
Ideally want to have a high base ratio? |
| What is spaciousness factor? | Ratio of indirect sound to total sound.
Greater the proportion of indirect sound the greater the spaciousness factor.
Ideally want a high spaciousness factor. |
| What are the cues used for separating sound sources? | Location.
Onset time.
Timbre and pitch.
Auditory continuity.
Experience. |
| How does location help segregation of sound sources? | Through use of interaural time difference and interaural level differences.
Strong cue. |
| How does onset time help segregation of sound sources? | If sounds begin at different times, they likely originate from different sources.
If sounds begin at the same time, they likely originate from the same source. |
| How does time and pitch help segregation of sound sources? | Can easily segregate instruments that have different timbres.
Can separate two of the same instrument based on pitch. |
| How does auditory continuity help segregation of sound sources? | Tones interrupted by silence are heard as distinct.
Tones interrupted by noise (or another stimulus) are heard as continuous.
Humans assume tones continue through the noise. |
| How does experience help segregation of sound sources? | You are more likely to be able to segregate two melodies if you have heard them before separately.
Same for noises. |
