noise pollution

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  • Assoc. Prof. Dr. Amirhossein Malakahmad

    Civil Engineering Department

    Universiti Teknologi PETRONAS

    CO3: To evaluate various sources of air and

    noise pollution and propose the relevant

    control principles.

  • Unit objectives

    At the end of this session you will be able to:

    Justify noise pollution and its importance.

    Evaluate noise pollution problems and causes.

    Calculate noise level emissions from single and combined sources.

  • Noise Definition

    Noise is an environmental pollutant, a waste product generated in conjunction with various

    anthropogenic activities.

    Noise is any sound (independent of loudness) that can produce an undesired physiological or

    psychological effect in an individual, and that

    may interfere with the social ends of an individual

    or group.

  • Noise pollution problems

    Noise of sufficient intensity and duration can induce temporary or permanent hearing loss, ranging from

    slight harm to nearly total deafness.

    In general, a pattern of exposure to any source of sound that produces high enough levels can result in

    temporary hearing loss. If the exposure persists over

    a period of time, this can lead to permanent hearing

    damage.

    It has been estimated that 1.7 million workers in the United States between 50 and 59 years of age have

    enough hearing loss to be awarded compensation.

  • Why noise pollution is taken for granted?

    Noise, if defined as unwanted sound, is a subjective experience. What is considered noise by one listener may be considered desirable by another.

    Noise has a short decay time and thus does not remain in the environment for extended periods, as do air and water pollution.

    To those persons whose hearing may already have been affected by noise, it may not be considered a problem at all.

  • Noise level calculations

  • Example 1 - Calculate the difference in

    dB If the second produces:

    a. twice as much power than the first,

    b. 10 times the power of the first,

    c. A million times the power of the

    first.

  • Measuring scale

    A scale based on the logarithm of the ratios of the measured quantities is used to calculate the noise. The unit for these types of measurement scales is the decibels (dB).

    L = level, decibels (dB)

    Q = measured quantity

    Q0= reference quantity

    log = logarithm in base 10

  • Combining sound pressure levels

    When sound pressure levels are combined the total level cannot be predicted by simply adding

    the levels.

    In terms of the basics, we need to work out the power that each level represents, add those

    powers together and turn the total back into a

    decibel figure.

    etcL

    LLL

    total101010

    321

    101010log10

  • Example 2 - What sound

    power level results from

    combining the following

    three levels: 68 dB, 79dB,

    and 75 dB?

  • Example 3 - A motorcyclist is warming up his racing

    cycle at a racetrack approximately 200 m from a

    sound level meter. The meter reading is 56 dB. What

    meter reading would you expect if 15 of the

    motorcyclist's competitors join him whit motorcycles

    having the same sound emission characteristics?

    Conduct your calculations via both sound level

    differences and sound combinations methods.