Sound

1. Sound Characteristics

2. Soundwaves Sound begins as a vibration Pythagorus and Hippocrates hypothesized this around 0 C.E. Sound travels through a medium Through air at about 1130 ft/sec Through water at about 4 Xs faster Through steel at about 20 Xs faster

3. Soundwaves Consist of waves of energy. Compression: when energy forces molecules closer together Rarefaction: when molecules are pulled farther apart into a partial vacuum Air Loss: Loss of energy due to friction of the sound wave through the air.

4. Sound Characteristics Frequency We interpret as pitch Frequency is the measure of how often a sound wave repeats itself Unit of measurement = Hertz (Hz) Human range of hearing � 20 Hz to 20,000 Hz Range of hearing depends on individual

5. Sound Characteristics Amplitude The energy of a soundwave Interpreted as loudness or volume Measured in decibels (dBs) 0 dB = threshold of hearing 120 dB = threshold of pain 60 dB = normal conversation

6. Sound Characteristics Waveform The graphic representation of a sound�s energy over time Simplest waveform is a sine wave

7. Sound Characteristics Phase The time relationship between two soundwaves Soundwaves are in-phase when they largely coincide in time (constructive interference) Soundwaves are out-of-phase when they largely don�t coincide in time (destructive interference)

8. Sound Characteristics Wavelength The length of a soundwave ? = V/f, where ? is wavelength, V is velocity of sound and f is frequency High frequencies have short wavelengths Low frequencies have long wavelengths

9. Sound Characteristics Harmonic Content Fundamental = lowest frequency present in a musical tone Overtones = all frequencies present in a musical tone other than the fundamental Harmonics = overtones that are whole number multiples of the fundamental Overtones largely responsible for timbre

10. Sound Characteristics Acoustic Envelope 1. Attack (how a sound starts) 2. Internal Dynamics (energy changes after the attack) 3. Decay (how a sound ends) Aids in identifying the sound source instrument Can be divided into more than three sections

11. Acoustics and Pschoacoustics Terminology Linearity = A comparison of how accurately a system�s output duplicates the input Masking = The hiding of one sound by another Complex waveform = A waveform comprised of simple soundwaves (sine waves)

12. Acoustics and Pschoacoustics Terminology Equal Loudness Principle = Equal amplitudes of different frequencies appear to be of unequal amplitudes Binaural Localization = Determining the direction of a sound source by using two ears Precedence Effect = We tend to determine the direction of a sound source from the first sound we hear Temporal Fusion = When a reflected sound occurs less than 30 milliseconds after the direct sound, we perceive the two sounds as one Reverb Decay Time = The time it takes a sound to decrease 60dB

13. Acoustics and Pschoacoustics Terminology

14. Reflected Sound Echo tells us about the size of the acoustic environment Reverb tells us about the texture of the acoustic environment Most of the energy we hear in sound lies in reverberation

15. ECHO Early reflections of sound Bounce off only one surface before reaching our ears Usually arrive less than 50 milliseconds after the direct sound

16. REVERB Later reflections of sound Bounce off more than one surface before reaching our ears Usually arrive after 50 milliseconds after the direct sound

17. The Ear Soundwaves first encounter the pinnae, the cartilage of the outer ear that directs or focuses sound down the ear canal The sound vibrations then reach the eardrum which passes them along to the middle ear

18. The Ear The middle ear (the ossicles) is composed of three tiny bones: the hammer, anvil, and stirrup The ossicles are designed to amplify the sound as it travels toward the inner ear The ossicles are also designed to prevent damage to the inner ear The stirrup is attached to the inner ear at the oval window

19. The Ear The inner ear�s largest structure is the cochlea which is filled with a fluid Within the fluid is a smaller structure called the Organ of Corti Upon the Organ of Corti are tiny cilia which transfer the sound vibrations directly to neural synapses which in turn send the information to the brain as electro-chemical impulses

20. Studio Design Much of studio design is motivated by a desire to better control the process of recording as well as the product We can better control the process and product by utilizing acoustic isolation and multi-track recording techniques

21. Studio Design To accomplish better sound isolation we often use double thick structures We also use floating floors and walls We avoid such structures as: Parallel surfaces Right angles Acute angles Concave surfaces