The reason helicopters are so loud is because of the massive blades that create a large vacuum and low air pressure in the wake of the aircraft. This air pressure is created by the air pressure around the pressurized side of the blade. This makes the helicopter’s noise so loud, that the name “Huey” has been given to this type of helicopter. This helicopter is a workhorse for the Army during the Vietnam War, and its noisy operation earned it the nickname.
Sound waves
Sound is always in the form of waves that move through a medium. They can be measured in terms of amplitude and frequency. The higher the amplitude, the louder the sound. However, sound is not the only medium where sound can travel. A small amount of air or water may also act as a medium.
Air, water, and rocks can all be affected by sound waves. This is because of the way sound travels. Air near the ground has a lower index of refraction than air above, which causes sound waves to bend toward the earth.
Rotor blades
When the Huey helicopter flies, the sound produced is so loud that it has been compared to the sound produced by a jet engine. The noise is produced by the rotor blades, and is particularly loud when they are rising. The main rotor generates most of the noise, as it causes the helicopter to rise, which creates a concentrated vortex. In addition to the noise produced by the main rotor, the tail rotor also produces a thumping sound. The sound becomes even more loud when the helicopter is approaching the listener.
The Huey helicopter first saw combat in Vietnam, where it served as a troop transport, medevac and armed assault helicopter. This helicopter was extremely fast and nimble, and it was the ideal aircraft for the Army as it was developing a concept called “air mobility.” This concept was a way to drop troops at strategic locations. The Huey was especially effective because it could fly very quickly and be escorted by a slow Pisecki H-21 Flying Banana.
Speed of rotor blades
The speed of rotor blades is one of the main reasons that helicopters are so loud. The speed of sound at ground level is 1100 fps, and the speed of sound at the tip of a helicopter’s rotors is 670 fps. This makes the helicopter’s blades sound supersonic. This is because the speed of sound at the tip of rotors is proportional to the square of the speed.
A variety of factors contribute to the noise generated by helicopter rotors. The speed of the blades, the air flow around the blade tips, and the amount of loading on the blades all contribute to the noise level. Torque control systems are designed to reduce this noise.
Operation of helicopters
While helicopters are a useful means of air transportation, there are a few ways to reduce the noise they produce. One method is to fly farther away from residential neighborhoods. At a distance of a thousand feet, an aircraft produces half the noise it would at a distance of 500 feet. Another method is to fly on different routes. By doing this, helicopters will make much less noise, which can reduce noise complaints.
Most of the noise produced by helicopters originates from their rotor blades. This is due to a process known as Blade Vortex Interaction, in which the blades of a helicopter encounter the air surrounding them and create a variety of noises. Other sources of noise include the engine and gear box, which produce a variety of up-close sounds.
Noise level of helicopters
Noise level of helicopters is an issue that affects public perceptions. The public’s response to helicopter noise depends on the amount of acoustic noise and the amount of “virtual noise” a helicopter emits. The acoustic noise is a measure of the helicopter’s noise level, and the virtual noise is the noise’s subjective characteristics as first perceived. The magnitude of virtual noise does not necessarily relate to the absolute noise level of helicopters, although it does account for the duration of the sound.
To determine the noise level of helicopters, the aircraft must fly within a certain radius, in order to be noise-free. Typically, the helicopter must be between 5.5 and 6.5 deg above the ground, which is known as the “flyover position”. For helicopters with smaller MTOWs, the minimum noise level will be lower than a helicopter of the same MTOW.
