Data Harvest 1145 Manuel - Sayfa 10

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Usage Information

Make sure the microphone end is placed so it points directly at the sound source.

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When using a 'Value Rises Above' or Higher than' condition to start logging it can be frustrating if

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classroom noise triggers a recording. It is often best to choose a higher trigger value than planned

with a pre-trigger time set so the start of an event is captured.

This sensor is not waterproof, it has an operating range of 0 to 95% RH (non-condensing). Do not

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place the sensor in an environment in which high humidity levels are possible as this may result in

damage or malfunction.

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If the sensor has been left in the cold, let it warm to near room temperature before waking it from

sleep.

Sound level (dBA and dBC ranges)

The unit of sound intensity level or loudness is the decibel (dB). The sensor can measure the sound

level in decibels using either the dBA or dBC range. The term dBA and dBC refer to the types of filters

used to measure the sound (dB) - either an A filter or a C filter.

The dBA range is the range most widely used as it indicates sound pressure level with 'A' weighting to

give a response similar to the normal human ear in the range and intensity that it 'hears' sounds, so a

noise which sounds louder will produce a larger dBA reading.

The response of the human ear to levels of loudness will vary with the frequency of the sound wave it is

detecting (frequency = sound vibrations produced per second). They are very sensitive in the frequency

range of approximately 500 to 6,000 Hz (mid-range frequencies) and much less sensitive to higher and

lower frequencies. The A weighing filter covers the full range of human hearing (high and low

frequencies sensitivity is reduced).

The dBC range is similar to A but it can also measure sounds whose frequency is outside the range of

normal human hearing particularly those sounds with very high (10,000 Hz +) or very low (<800 Hz)

sound pressure/frequency levels. The 'C' weighting is useful for measuring high level noise such as

engines and machinery.

The loudness of a sound depends on the amplitude of the sound waves. Increasing the 'volume' of a

radio increases the amplitudes of the sound waves produced by the radios speaker, so the sound from

the radio is louder.

Changing the loudness does not alter the frequency of a sound.

Sound Level (dB)

Above 120

100

80 to 90

Waveform ranges (mV)

The Waveform range has a maximum frequency response between 20 to 10,000 Hz (10 kHz), its

sensitivity then reduces for sound with a frequency between 10 kHz to 16 kHz. It is used for examining

the frequency content of sound.

Sound waves are longitudinal. As sound passes through the air, the air particles oscillate about fixed

Perceived loudness at frequency of 1,000 Hz

Threshold of pain

Very noisy (Rock concert, Helicopter)

Loud (Hair dryer, Lawnmower, medium truck).

This is the level at which employers must provide hearing protection

Moderate (passenger car)

Moderately to quiet (Normal conversation)

Very soft (Light rain, Quiet living room)

Faint (library)

Threshold of hearing

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1145 - Wireless Sound Level Sensor