PSM Made Easy

NOISE and HEALTH

Environment and Health

  • NOISE- Unwanted sound
  • Come to be a major “stress factor” in today’s life
    • Noise Pollution = unwanted or excessive sound that can have damaging effects on human health,
  • Sources of noise are varied:
    • Automobiles
    • Factories
    • Air crafts etc.
  • Levels particularly high around:
    • Railway junctions,
    • Bus depots
    • Airports
    • High Traffic areas etc.

• Noise has 2 characteristics:

  1. Intensity or loudness

  2. Frequency

  3. Intensity (Loudness)

  • Measured in decibels (dB)
    • 60 dB sound means, 60 dB more intense then the lowest discernible noise (=reference)
  • dBA is used instead of dB in case of human hearing as human responds not to the REAL loudness but to a PERCEIVED intensity.
  • dB (A) denotes the perception of sound by the normal human ear
  • dBA is calculated by ‘A’ using A weighted curve k/a ‘curve A’ which has been constructed to take into account, the subjective effect of the sound on a normal ear

2. Frequency:

  • Measured in Hz
    • Human ear can identify 20 to 20,000 Hz
    • < 20 Hz = infra-audible

    • 20,000 Hz = Ultra-sonic

    • Some animals can hear sounds inaudible to human ear
    • Phon: is an index of intensity whilst also taking into account, the frequency

Some Everyday Sound Levels

Source of noise Sound level (dB)
Whisper 20
Speech b/w 2-3 people 73
Speech on radio 80
Music on radio 85
Children shouting 79
Children crying 80
Vacuum cleaner 76
Piano 86
Jet take-off 150
Original image

Some everyday noise levels

Acceptable Levels of Noise

Residential Bed room 25 dBA
Living room 40 dBA
Commercial Office 35 – 45 dBA
Conference 40 – 45 dBA
Restaurants 40 – 60 dBA
Industrial Workshop 40 – 60 dBA
Laboratory 40 – 50 dBA
Educational Class room 30 – 40 dBA
Library 35 – 40 dBA
Hospitals Wards 20 – 35 dBA
Original image

Some acceptable levels of sound

Cut-off levels of sounds
cut off levels of noise

Instruments used in Studying Noise
1. Sound level meter:

  • Measures intensity of sound in dB or dBA

2. Octave band frequency analyzer:

  • Measures noise in octave bands
    • Creates a plot showing the ‘sound spectrum’
    • Indicates the characteristics of the noise
  • Mainly high pitch
  • Mainly low pitch or
  • Variable pitch

3. Audiometer:

  • Machine used for evaluating hearing capability
    • Zero line at the top of audiogram represents normal hearing.
    • Noise induced hearing loss shows a characteristic dip in the curve at the 4000 Hz frequency

Health Effects of NOISE

  1. Auditory
  2. Non – Auditory

Auditory effects
Auditory fatigue: whistling and buzzing in ears

  • Appears at 90 dB and affects most the frequency of 4000 Hz

Deafness or hearing loss

  • Victim usually unaware esp. initial stages
  • Temporary/ permanent

Temporaryhearing loss

  • Exposure to one episode of loud noise
  • Disappears after some time (up to 24 hr.) following the exposure
  • Most affected frequency: 4000 – 6000 Hz

Permanenthearing loss

  • Repeated /continuous exposure to 100 dB
  • Occupational hearing loss is due to this
  • Exposure to > 160 dB may even rupture the tympanic membrane

Non – Auditory Effects of Noise Exposure

  • Interference with speech: speech level needs to exceed ambient sound by 12 dB
  • Annoyance
  • Efficiency reduction
  • Physiological changes
    • Stress hormones
    • Rise in BP
    • Rise in intracranial pressure
    • Increase in heart rate
    • Interference in sleep

Economic loss

  • Less productivity: reduced efficiency, workers in noisy conditions have been found to be more irritated, short fuse and quicker to agitate and halt production
    • Occupational health claims to industry

Control of Noise Pollution
1. Cautious planning of cities

  • Separate industrial and transport zone
    • Separation of residential areas from main streets by green belts
    • Houses not < 15 m from main street, thick plantation
    • Widening of main streets

2. Control of vehicles

  • Heavy vehicles not allowed in narrow streets
    • Prohibit indiscriminate blowing of horn

Reference

  • Park’s Textbook of PSM. 25th ed. 2019 Bhanot Publishers, Jabalpur
  • Mathias Basner, Wolfgang Babisch, Prof. Adrian Davis, Mark Brink, Charlotte Clark, Sabine Janssen, Prof. Stephen Stansfeld Auditory and non-auditory effects of noise on health .Lancet. 2014 Apr 12; 383(9925): 1325–1332
  • Stephen A Stansfeld and Mark P Matheson. Noise pollution: non-auditory effects on health British Medical Bulletin 2003; 68: 243–257