This change in reactivity is regarded as the result of sensitization toward the special type of noise and the implications of these observations for the long-term effects of chronic exposure to low-altitude flight noise are considered. At high intensities and fast level increase an up to fourfold reaction intensification was detected in the majority of subjects. The blood pressure response to a repeated single exposure increased in proportion to the preceding noise exposure. In order to prevent risks to the subjects' health, the noise exposure was not raised to levels above 112 dB(A) and fast level increase, although Lmax = 125 dB(A) has been measured in 75 m-low-altitude flight areas. The systolic and diastolic blood pressure was raised at Lmax = 112 dB(A) and high speed level increase at the average of 23 and 13 mmHg, respectively with individual maximal values of about 40 mm Hg (systolic). They were exposed to the noise of two to three overflights with Lmax = 99-114 dB(A) and slow sound pressure level increase (aircraft take off) or with Lmax = 95-112 dB(A) and a fast sound pressure level increase (low-altitude flight at high subsonic speed) at intervals of 10 to 15 min. A high-quality recording and reproduction technique was employed. Their blood pressure and heart rates were measured simultaneously. According to the National Lightning Safety Institute, thunder is seldom heard beyond 10 miles under ideal conditions.Volunteers aged 70 to 89 years living in a senior citizen's home in Haifa were exposed to flight noise via earphones while watching video films. The shock wave extends out about 30 feet then changes into the ordinary sound wave we know as thunder. What happens is lightning super heats the air around it which causes a sudden increase in pressure and causes surrounding air to expand violently at a rate faster than the speed of sound which creates a shock wave which expands outward from the lightning bolt. Thunder: A sonic boom created by a plane sounds similar to thunder because thunder is also a sonic boom. Here’s a pretty cool compilation of jets creating sonic booms: As an aircraft flies at supersonic speeds it is continually generating shock waves, dropping sonic boom along its flight path, similar to someone dropping objects from a moving vehicle. These waves travel at the speed of sound, and as the speed of the aircraft increases the waves are forced together, or compressed, because they cannot “get out of the way” of each other, eventually merging into a single shock wave at the speed of sound. This is because as an object passes through the air, it creates a series of pressure waves in front of it and behind it, similar to the bow and stern waves created by a boat. Sonic Boom: A sonic boom can be created when a plane goes faster than the speed of sound. Of course, the speed of sound depends on how high above sea level the plane is and what the temperature is. At Mach 2 the plane would be traveling at twice the speed of sound. Thus, at Mach 1, a plane would be traveling exactly equal to the speed of sound. Mach:“Mach” is how fast with reference to the speed of sound something (usually a plane) is traveling. Here’s a helpful chart (note that 447 meters per second is 1,000 mph): Solids: Sound speed can vary greatly in solids.The speed of sound increases in water with temperature and pressure. Water: Sound travels at 3,315 mph through water at 46☏.At 30,000 feet speed of sound is about 678 mph. At 32 degrees at sea level the speed of sound is 742 mph. Air: At sea level at 59 degrees with zero humidity sound travels just a tad over 761 mph.Thus, temperature affects the speed of sounds, as does pressure. The closer the molecules are to each other and the tighter their bonds, the faster sound travels. What is the speed of sound? That depends on what medium it is traveling through. So, there is no sound in a vacuum such as space (all those explosions in sci-fi movies are actually silent!). Thus, in order for sound to travel it must be transported through a medium capable of conducting waves, such as a gas, liquid or solid. It is kinetic energy that travels from molecule to molecule. Sound is generated by a vibrating object acting on molecules around it and travels as waves.
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