The Nature of Sound

Discussion

introduction

Sound is a longitudinal, mechanical wave.

Sound can travel through any medium, but it cannot travel through a vacuum. There is no sound in outer space.

Sound is a variation in pressure. A region of increased pressure on a sound wave is called a compression (or condensation). A region of decreased pressure on a sound wave is called a rarefaction (or dilation).

[slide]

The sources of sound

What are the different characteristics of a wave? What are the things that can be measured about waves? Amplitude, frequency (and period), wavelength, speed, and maybe phase. Deal with each one in that order.

amplitude, intensity, loudness, volume

Amplitude goes with intensity, loudness, or volume. That's the basic idea. The details go in a separate section.

[ISO 226:2003]

speed of sound

The speed of sound depends upon the type of medium and its state. It is generally affected by two things: elasticity and inertia.

gases liquids
v = √  K  = √  γP  = √  γkT
ρ ρ M
v = √  K
ρ
K =  bulk modulus K =  bulk modulus
ρ =  density ρ =  density
γ =  cP/cV (specific heat ratio) solids
P =  absolute pressure
v = √  E
ρ
k =  boltzmann's constant
T =  absolute temperature E =  young's modulus
M =  molecular mass ρ =  density

Acoustic Thermometry of Ocean Climates (ATOC)

echoes

scraps

solids v (m/s)   liquids v (m/s)
aluminum 6420   alcohol, ethyl 1207
beryllium 12,890   alcohol, methyl 1103
brass 4700   mercury 1450
brick 3650   water, distilled 1497
copper 4760   water, sea 1531
cork 500   gases (STP) v (m/s)
glass, crown 5100   air, 000 ℃ 331
glass, flint 3980   air, 020 ℃ 343
glass, pyrex 5640   argon 319
gold 3240   carbon dioxide 259
granite 5950   helium 965
iron 5950   hydrogen (H2) 1284
lead 2160   neon 435
lucite 2680   nitrogen 334
marble 3810   nitrous oxide 263
rubber, butyl 1830   oxygen (O2) 316
rubber, vulcanized 54   water vapor, 134 ℃ 494
silver 3650   biological materials v (m/s)
steel, mild 5960   soft tissues 1540
steel, stainless 5790      
titanium 6070      
wood, ash 4670      
wood, elm 4120      
wood, maple 4110      
wood, oak 3850      
Speed of sound in various materials Source: probably an old version of the CRC

frequency, pitch, tone

The frequency of a sound wave is called it pitch. High frequency sounds are said to be "high pitched" or just "high"; low frequency sounds are said to be "low pitched" or just "low".

f (THz) device, event, phenomena, process
0.1–2 SASER (sound laser)
f (MHz) device, event, phenomena, process
1–20 medical ultrasound
f (kHz) device, event, phenomena, process
25–80 bat sonar clicks
40–50 ultrasonic cleaning
32.768 quartz timing crystal
18–20 upper limit of human hearing
4–5 field cricket (Teleogryllus oceanicus)
2.2–2.8 clapping
2–5 maximum sensitivity of the human hear
f (Hz) device, event, phenomena, process
300–3000 voice frequency (VF), important for understanding speech
2048 C7 scientific scale, highest note of a soprano singer (approximate)
440 A4 american standard pitch, tv test pattern tone
435 A4 international pitch
426.67 A4 scientific scale
261.63 C4 american standard pitch
258.65 C4 international pitch
256 C4 scientific scale, typical fundamental frequency for female vocal cords
128 C3 scientific scale, typical fundamental frequency for male vocal cords
64 C2 scientific scale, lowest note of a bass singer (approximate)
90 ruby-throated hummingbird in flight
60 alternating current hum (US and Japan)
50 alternating current hum (Europe)
8–20 lower limit of human hearing
17–30 blue and fin wales are the loudest marine sounds in this range
1–5 tornadoes
Frequency of Selected Sounds

human hearing and speech

Humans are generally capable of hearing sounds between 20 Hz and 20 kHz (although I can't hear sounds above 13 kHz). Sounds with frequencies above the range of human hearing are called ultrasound. Sounds with frequencies below the range of human hearing are called infrasound.

More in the next section.

infrasound

ultrasound

  frequency
(MHz)
power
(W)
intensity
(W/cm2)
pulse
duration
imaging, echo 1 20 0.05 1.75 0.2 1 μs
imaging, doppler 1 20 0.15 15.7 0.3 10 μs
physiotherapy 0.5 3 < 3 2.5 continuous
surgery 0.5 10 ~ 200 1,500 1 16 s
Typical parameters used for medical ultrasound Source: Physics Today
fish actinopterygii frequency range (Hz)
american shad Alosa sapidissima 200 180,000
goldfish Carassius auratus 5 2,000
atlantic cod Gadus morhua 2 500
tuna Thunnus … 50 1,100
catfish … … 50 4,000
amphibians amphibia frequency range (Hz)
tree frog … … 50 4,000
bullfrog Lithobates catesbeianus 100 2,500
cave salamander Proteus anguinus 10 10,000
reptiles reptilia, sauropsida frequency range (Hz)
red-eared slider Trachemys scripta elegans 68 840
spectacled caiman Caiman crocodilus 20 6,000
birds aves frequency range (Hz)
mallard duck Anus platyrhynchus 300 8,000
pigeon Columba livia ? 5,800
chicken Gallus gallus 125 2,000
canary Serinus canaria 250 8,000
cockatiel Nymphicus hollandicus 250 8,000
parakeet Melopsittacus undulatus 200 8,500
penguin Spheniscus demersus 100 15,000
owl … … 200 12,000
mammals mammalia frequency range (Hz)
cattle Bos taurus 23 35,000
sheep Ovis aries 100 30,000
pig Sus scrofa domestica 45 45,000
dog Canis lupus familiaris 67 45,000
cat Felis silvestris catus 45 64,000
ferret Mustela putorius furo 16 44,000
raccoon Procyon lotor 100 40,000
blue whale Balaenoptera musculus 5 12,000
humpback whale Megaptera novaeangliae 30 28,000
risso's dolphin Grampus griseus 8,000 100,000
beluga whale Delphinapterus leucas 1,000 123,000
atlantic bottlenose dolphin Tursiops truncatus 75 150,000
greater horseshoe bat Rhinolophus ferrumequinum 2,000 110,000
jamaican fruit bat Artibeus jamaicensis 2,800 131,000
northern quoll Dasyurus hallucatus 500 40,000
opossum … … 500 64,000
hedgehog … … 250 45,000
rabbit … … 360 42,000
horse Equus caballus 55 33,500
japanese macaque Macaca fuscata 28 34,500
old world monkeys … … 60 40,000
human Homo sapiens 31 17,600
asian elephant Elephas maximus 16 12,000
guinea pig Cavia porcellus 54 50,000
chinchilla Chinchilla lanigera 90 22,800
hamster Mesocricetus auratus 80 45,000
rat Rattus … 500 64,000
mouse Mus … 2,300 85,500
gerbil Meriones unguiculatus 100 60,000
manatee Trichechus manatus latirostris 400 46,000
insects - insecta frequency range (Hz)
noctuid moth … … 1,000 240,000
grasshopper … … 100 50,000
Frequency Hearing Ranges for Selected Animals (60 dB)