The softest sound heard by the human ear is 0.0000000000000001 watts and the most piercing is 0.0001 watts - a scale of 10,000,000,000, or 1010. Noise has been defined as unwanted higher volume sound with no meaning and that is usually obstructive of communication. These tips will help you learn about noise levels and how to do sound measurement.
Why measure? Since noise interferes with meaningful communication, the need is to reduce or remove it. Understanding the degree of the problem (does it exist?) is the initial step and will provide a guide to acting on it (determining noise exposure levels, etc). Noise is measured when its characteristics are quantified. Measures of noise would include sound pressure magnitude and frequency content, loudness, pitch and fluctuation strength. The decision to use a metric measurement method would depend on the application, for example, isolating source emission, hearing conservation, outside environmental noise, interior room noise, etc. Measuring for compliance to meet a statutory standard would be different from that intended for comfort.
Steps to measure noise.
- Determine sound measurement items like a sound pressure level for comparison against a reference value and the noise for frequency analysis
- Determine the nature and origins of the noise, the regularity and span, conditions in which it spreads and the strength of the noise to inflict hurt. Also identify any additional peripheral noises.
- While planning, equipment, procedure and points of measurement, communication process, noise seepage, etc., must be examined in view of the measurement objective.
Requirements for measurement.
- Tools. Keep a list of necessary apparatus including batteries, power cables, timers, tripods, transceivers, etc., handy and do a dry run with the equipment prior to actual measurement. Frequently used tools are the sound level meter (SLM) for noise levels caused by a discrete source and noise surveys, the noise dosimeter for personal noise exposure and the integrating sound level meter (ISLM). The user's manual will provide details on calibration, operation and interpreting readings.
- Documents and records. Have papers on site details, maps, etc., to facilitate measurement points and records of weather conditions, measurement range, and so forth.
- A team which is well informed on the plan and prepared with necessary tools
Creating ideal conditions. Make sure to take the following steps or have the itemized equipment below to ensure your test goes through cleanly and you get the correct data to measure the noise levels.
- Wind prevention screen for protecting the noise level meter microphone.
- The site should be free from magnetic fields, vibrations, severe temperature or humidity.
- The time selected for measurement must be when peripheral sounds are constant.
- Based on an approximation of the A-weighted sound pressure level, set the full range for the measurement time and keep a watch for overloads.
- Ensure regular recording of target sound, noise, environment variation details etc. Where the measurer at the source does not have view of the border parts, then a team member must be stationed at the border with regular communication on valuable details.
- Identify recording spots on the notes and substantiate positions through site photographs.
- Ensure there are no interruptions or noise from the measurement team.
- Noise figures are relative to the way it has been measured and International standards are set for measurement, control and declaration of noise in specific areas.
What remains is to ask yourself what can be done to help--steps to reduce noise, report noise issues and use ear guards. Happy listening!