Physical properties of sound
Speed of sound c (m/s)
The speed of sound is dependent on the mass and elasticity of the medium; in general sound travels faster in solids than in liquids and faster in liquids than in gases.
The speed of sound in air depends on temperature; in lower temperatures it travels slower; however for architectural acoustics the speed of sound in 20°C which is 340 m/s is used.
Sound speed in different materials
| Materials | Sound speed (m/s) |
| Rubber | 35-230 |
| Mantar | 480 |
| Air (20°C) | 330 / 340 / 350 |
| Water | 1400 |
| Wood | 1000-4000 |
| Marble | 3800 |
| Concrete | 3500-5000 |
| Glass | 4000-5000 |
| Steel | 5000 |
Sound can be defined by its three components; frequency, wavelength and period.
Frequency f(Hz)
The number of cycles per second is called the frequency. The unit of frequency is Hertz
1 Hz = 1 cycle/sec
Sound is 10 octaves bands; 16-32-64-125-250-500-1000-2000-4000-8000-16000 Hz
Humans sensitivity to sounds depends on frequency; we are most sensitive to sounds having significant energy in the 500 to 4 000 Hz.
Wavelength l (m)
Wavelength is the distance between two successive pressure maxima or between successive minima in a plane wave.
l =c/f
High frequencies have short wavelengths (the l of 4000Hz is 0,085 m)
Low frequencies have long wavelengths (the l of 125 Hz is 2,7 m)
Period T (s)
The time that it takes for the sound wave to start repeating itself is called period. Period is the duration of one vibration
T=1/f
High pitched sounds have fast vibrations;
Low pitched sounds have slow vibrations
Quantity
| Symbol (Unit) | Lowest sound | Highest sound |
Frequency f (Hz) | 16 Hz Low frequency | 16000 (20000) Hz High frequency |
| Period T (s) | 1/16 s Slow vibrations | 1/16000 (20000)s Fast vibrations |
| Wavelength I (m) | ≈ 20 cm Long waves | ≈ 0,02 m Short waves |
