Complex sounds, decibels and psychoacoustics

• the sounds that we hear
• -they have a combination of many different frequencies each with its own amplitude and phase
• -can be periodic or aperiodic

• aperiodic sound that has random sound waves. 
• -it can be transient (brief or short duration) or
• -it can be turbulent (continuous)

white noise-it should be flat when we measure it with equal energies across frequencies. used to calibrate a speaker or microphone

time, frequency and intensity

a measure of amplitude by time. difficult to pick out specific frequencies

good for showing specific frequencies and intensities but can not see changes over time

any complex wave can be analyzed to determine the amplitude, frequency and phases of the sinusoidal components

• fundamental frequency: lowest freq of a complex sound (not found in aperiodic sounds)
• harmonics:a whole number multiple of the fundamental freq ex fundamental is 100Hz it will contain harmonics of 200hz 300hz etc. but each may have different amplitudes

as things become more stiff or less massive they resonant at a higher frequency.

is its favourite vibrating frequencies due to mass and stiffness

• stiffness opposes low Hz vibrations (ossicle ossification)
• mass opposes high Hz vibrations (ear infection)
• as we go up in stiffness resonance goes up
• as we go up in mass we go down in resonance frequency

• looks at what is received on a diaphragm
• -measured in upa, 20upa smallest pressure required for a human with normal hearing to hear 1000Hz tone

• changes upa to dB SPL
• 20Xlog(p1/pref) 
• pref=20

• 20 X log(p1/p2)
• comparing two different pressure values

• the study of the relationship between physical stimuli and psychological response
• measures sound by pitch loudness and localization

describes how high or low a sound is perceived. In general is rises as Hz rises

subjective experience associated with sound pressure (amplitude)

in order for a sound to be perceived as louder you need to increase the intensity. In order for people to perceive different freq as the same established anchor or reference tone you need to increase the intensity. more for lower freq

• the ability to determine where sound is coming from.
• -our ears use intensity and phase differences to determine location.
• High freq- intensity cues
• low freq- phase cues