Today, many new settlers, arranging an apartment, are forced to conduct additional work, including sound insulation of their home, because The standard materials used make it possible to only partially hide what is happening in their own home, and not to be interested in the will of neighbors.
The speed of sound in solids is affected at least by the density and elasticity of the substance opposing the wave. Therefore, when equipping the rooms, the layer adjacent to the supporting wall is made soundproof with "overflows" from above and below. It allows you to reduce the noise level in decibels sometimes more than 10 times. Then lay basalt mats, and on top - plasterboard sheets that reflect the sound outside the apartment. When the sound wave "flies" towards such a design, it damps out in the layers of the insulator, which are porous and soft. If the sound is of great strength, then the materials absorbing it can even heat up.
Elastic substances, such as water, wood, metals, transmit sound vibrations well, so we hear the beautiful "singing" of musical instruments. And some nationalities in the past determined the approach, for example, of riders, putting the ear to the ground, which is also quite elastic.
The speed of sound in km depends on the characteristics of the environment in which it propagates. In particular, the process can be affected by its pressure, chemical composition, temperature, elasticity, density and other parameters. For example, in a steel sheet a sound wave passes at a speed of 5100 meters per second, in the glass - about 5000 m / s, in a tree and granite - about 4000 m / s. To translate the speed in kilometers per hour, multiply the indicators by 3600 (seconds per hour) and divide by 1000 (meters per kilometer).
The sound velocity in km in an aqueous medium is different for substances with different salinity. For fresh water at a temperature of 10 degrees Celsius, it is about 1450 m / s, and at a temperature of 20 degrees Celsius and the same pressure - about 1490 m / s.
The salty medium differs by a much higher speed of passage of sound vibrations.
The propagation of sound in air also depends on temperature. With this parameter equal to 20 degrees Celsius, sound waves travel at a speed of about 340 m / s, which is about 1200 km / h. And at zero degrees, the speed slows to 332 m / s. Returning to our isolators for an apartment, we can learn that in a material such as a cork, which is often used to reduce the level of external noise, the speed of sound in km is only 1800 km / h (500 meters per second). This is ten times lower than this characteristic in steel parts.
The sound wave is a longitudinal vibration of the medium in which it propagates. When you pass, for example, the melody of a piece of music through an obstacle, the level of its volume decreases; The amplitude of the oscillations changes . At the same time, the frequency remains the same, due to which we hear a female voice as female, and male as a male voice. The most interesting is the place where the speed of sound in km is close to zero. This is a vacuum in which waves of this type almost do not propagate. To demonstrate how this works, physicists place a ringing alarm clock under the hood, from which the air is pumped out. The more rarefied the air, the quieter the bell is heard.