Tupolev 154M noise asesment (Анализ шумовых характеристик самолёта Ту-154М)

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    Тип работы: Диплом
    Тема: Tupolev 154M noise asesment (Анализ шумовых характеристик самолёта Ту-154М)

    Contents

    1 The Noise Problem

    2 Effects of Noise

    2.1 Hearing Loss

    2.2 Noise Interference

    2.3 Sleep Disturbance

    2.4 Noise Influence on Health

    3 Noise Sources

    3.1 Jet Noise

    3.2 Turbomachinery Noise

    4 Noise Measurement and Rules

    4.1 Noise Effectiveness Forecast (NEF)

    4.2 Effective Perceived Noise Level (EPNL)

    5 Noise Certification

    5.1 Noise limits

    6 Calculations

    6.1 Tupolev 154M Description

    6.2 Noise calculations

    6.2.1 Take-off Noise Calculation

    6.2.2 Landing Approach Noise Claculation

    7 Noise Suppression

    7.1 Jet Noise Suppression

    7.2 Duct Linings

    7.2.1 Duct Lining Calculation

    1The Noise Problem

    Though long of concern to neighbors of major airports, aircraft noise first became a major problem with the introduction of turbojet-powered commercial aircraft (Tupolev 104, Boeing

    707, Dehavilland Comet) in the late 1950s. It was recognized at the time that the noise levels produced by turbojet powered aircraft would be unacceptable to persons living under the

    take-off pattern of major airports. Accordingly, much effort was devoted to developing jet noise suppressors, with some modest success. Take-off noise restrictions were imposed by some

    airport managements, and nearly all first-generation turbojet-powered transports were equipped with jet noise suppressors at a significant cost in weight, thrust, and fuel

    consumption.

    The introduction of the turbofan engine, with its lower jet velocity, temporarily alleviated the jet noise problem but increased the high-frequency turbomachinery noise, which became a

    severe problem on landing approach as well as on take-off. This noise was reduced somewhat by choosing proper rotor and stator blade numbers and spacing and by using engines of the

    single-mixed-jet type.

    2Effects Of Noise

    Noise is often defined as unwanted sound. To gain a satisfactory understanding of the effects of noise, it would be useful to look briefly at the physical properties of sound.

    Sound is the result of pressure changes in a medium, caused by vibration or turbulence. The amplitude of these pressure changes is stated in terms of sound level, and the rapidity with

    which these changes occur is the sound\'s frequency. Sound level is measured in decibels (dB), and sound frequency is stated in terms of cycles per second or Hertz (Hz). Sound level in

    decibels is a logarithmic rather than a linear measure of the change in pressure with respect to a reference pressure level. A small increase in decibels can represent a large increase in

    sound energy. Technically, an increase of 3 dB represents a doubling of sound energy, and an increase of 10 dB represents a tenfold increase. The ear, however, perceives a 10-dB increase

    as doubling of loudness.

    Another important aspect is the duration of the sound, and the way it is distributed in time. Continuous sounds have little or no variation in time, varying sounds have differing

    maximum levels over a period of time, intermittent sounds are interspersed with quiet periods, and impulsive sounds are characterized by relatively high sound levels and very short

    durations.

    The effects of noise are determined mainly by the duration and level of the noise, but they are also influenced by the frequency. Long-lasting, high-level sounds are the most damaging

    to hearing and generally the most annoying. High-frequency sounds tend to be more hazardous to hearing and more annoying than low-frequency sounds. The way sounds are distributed in time

    is also important, in that intermittent sounds appear to be somewhat less damaging to hearing than continuous sounds because of the ear\'s ability to regenerate during the intervening

    quiet periods. However, intermittent and impulsive sounds tend to be more annoying because of their unpredictability.

    Noise has a significant impact on the quality of life, and in that sense, it is a health problem. The definition of health includes total physical and mental well-being, as well as the

    absence of disease. Noise is recognize...

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