The Physics
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Opus in profectus

The Nature of Sound

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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).

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. This is the Newton-Laplace equation. Laplace added the γ (gamma) correction factor for ideal gases.

solids

v = √ E
ρ
E =  Young's modulus
ρ =  density

fluids

v = √ K
ρ
K =  bulk modulus
ρ =  density

ideal gases

v = √ K  = √ γP  = √ γRT  = √ γkT
ρ ρ M m
K =  bulk modulus
γ =  cP/cV specific heat ratio
P =  absolute pressure
ρ =  density
T =  absolute temperature
R =  gas constant
M =  molar mass
k =  Boltzmann constant
m =  molecular mass

Acoustic Thermometry of Ocean Climates (ATOC)

echoes

scraps

Speed of sound in various materials Source: probably an old version of the CRC
solids v (m/s) liquids v (m/s)
aluminum 6,420 alcohol, ethyl 1,207
beryllium 12,890 alcohol, methyl 1,103
brass 4,700 mercury 1,450
brick 3,650 water, distilled 1,497
copper 4,760 water, sea 1,531
cork 500 gases (STP) v (m/s)
glass, crown 5,100 air, 000 ℃ 331
glass, flint 3,980 air, 020 ℃ 343
glass, pyrex 5,640 argon 319
gold 3,240 carbon dioxide 259
granite 5,950 helium 965
iron 5,950 hydrogen (H2) 1,284
lead 2,160 neon 435
lucite 2,680 nitrogen 334
marble 3,810 nitrous oxide 263
rubber, butyl 1,830 oxygen (O2) 316
rubber, vulcanized 54 water vapor, 134 ℃ 494
silver 3,650 biological materials v (m/s)
steel, mild 5,960 soft tissues 1,540
steel, stainless 5,790    
titanium 6,070    
wood, ash 4,670    
wood, elm 4,120    
wood, maple 4,110    
wood, oak 3,850    

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

Typical parameters used for medical ultrasound Source: Physics Today
  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
Frequency hearing ranges for selected animals (60 dB)
fish actinopterygii frequency range (Hz)
american shad Alosa sapidissima 200 180,000m
goldfish Carassius auratus 5 2,000m
atlantic cod Gadus morhua 2 500m
tuna Thunnus … 50 1,1001
catfish … … 50 4,0001
amphibians amphibia frequency range (Hz)
tree frog … … 50 4,0001
bullfrog Lithobates catesbeianus 100 2,5002
cave salamander Proteus anguinus 10 10,000i
reptiles reptilia, sauropsida frequency range (Hz)
red-eared slider Trachemys scripta elegans 68 8402
spectacled caiman Caiman crocodilus 20 6,000a
birds aves frequency range (Hz)
mallard duck Anus platyrhynchus 300 8,000b
pigeon Columba livia ? 5,8002
chicken Gallus gallus 125 2,0001
canary Serinus canaria 250 8,0001
cockatiel Nymphicus hollandicus 250 8,0001
parakeet Melopsittacus undulatus 200 8,5001
penguin Spheniscus demersus 100 15,000c
owl … … 200 12,0001
mammals mammalia frequency range (Hz)
cattle Bos taurus 23 35,0001,k
sheep Ovis aries 100 30,0001
pig Sus scrofa domestica 45 45,0002
dog Canis lupus familiaris 67 45,0001,2
cat Felis silvestris catus 45 64,0001,4
ferret Mustela putorius furo 16 44,0001
raccoon Procyon lotor 100 40,0001
blue whale Balaenoptera musculus 5 12,000d
humpback whale Megaptera novaeangliae 30 28,0004
risso's dolphin Grampus griseus 8,000 100,000j
beluga whale Delphinapterus leucas 1,000 123,0001
atlantic bottlenose dolphin Tursiops truncatus 75 150,0001,4
greater horseshoe bat Rhinolophus ferrumequinum 2,000 110,0001,4
jamaican fruit bat Artibeus jamaicensis 2,800 131,000e
northern quoll Dasyurus hallucatus 500 40,000f
opossum … … 500 64,0001
hedgehog … … 250 45,0001
rabbit … … 360 42,0001
horse Equus caballus 55 33,5001,k,l
japanese macaque Macaca fuscata 28 34,5002
old world monkeys … … 60 40,000g
human Homo sapiens 31 17,6002
asian elephant Elephas maximus 16 12,0001
guinea pig Cavia porcellus 54 50,0001,2
chinchilla Chinchilla lanigera 90 22,8001
hamster Mesocricetus auratus 80 45,0002
rat Rattus … 500 64,0002
mouse Mus … 2,300 85,5002
gerbil Meriones unguiculatus 100 60,0001
manatee Trichechus manatus latirostris 400 46,000h
insects - insecta frequency range (Hz)
noctuid moth … … 1,000 240,0003
grasshopper … … 100 50,0003
molluscs - mollusca frequency range (Hz)
pacific oyster Magallana gigas 10 1,000n
Major sources:
  1. Frequency hearing ranges in dogs and other species. George M. Strain. Deafness in Dogs and Cats. Louisiana State University (2003).
  2. Hearing ranges of laboratory animals. Henry E. Heffner and Rickye S. Heffner. Journal of the American Association for Laboratory Animal Science. Vol. 46 No. 1 (2007): 20–22.
  3. Amazing animal senses. Eric H. Chudler. Neuroscience for Kids. University of Washington.
  4. Strike a Chord - Hearing Ranges [dead link]. Questacon, Australia's National Science & Technology Centre.