The sound of human speech is mainly in the range 300 to 3,000 Hz. A healthy, young person can hear sounds with frequencies from roughly 20 to 20,000 Hz. High-pitched or treble sounds have high frequencies. Low pitched or bass sounds have low frequencies. The pitch depends also, in a lower degree, on the sound level and on the physiology of the auditory system. The Oxford Dictionary defines pitch as 'the quality of a sound governed by the rate of vibrations producing it the degree of highness or lowness of a tone.' Since the pitch is determined mostly by frequency, it is usually identified with it. The Harvard Dictionary of Music defines the pitch as a 'stretch of sound whose frequency is clear and stable enough to be heard as not noise'. The unit for frequency is the hertz (Hz = 1 cycle per second: Figure 1 shows one cycle from an air compression to a minimum pressure and back to a maximum pressure). In other words, frequency is the number of times per second that a vibrating body completes one cycle of motion. complete cycles of high and low pressure regions. What are pitch and frequency? Back to topįrequency is the rate at which the source produces sound waves, i.e. The properties of noise which are important in the workplace are: What are some properties of noise that can be measured? Back to top If there is a noise problem in a workplace, then a noise assessment or survey should be undertaken to determine the sources of noise, the amount of noise, who is exposed and for how long.

Does a person who has worked in a noisy workplace for years have problems understanding conversations at parties, or restaurants, or in crowds where there are many voices and 'competing' noises?.Do they find when they return home from work that they have to increase the volume on their car radio higher than they did when they went to work?.Do people who work in noisy environments have ringing in their ears at the end of a shift?.If you answer yes to any of the following questions, the workplace may have a noise problem. How can I tell if my workplace is too loud? Back to top Personal protection, however, should be considered as an interim measure while other means of reducing workplace noise are being explored and implemented.Īs a first step in dealing with noise, workplaces need to identify areas or operations where excessive exposure to noise occurs. Where technology cannot adequately control the problem, personal hearing protection (such as ear muffs or plugs) can be used. The best method of noise reduction is to use engineering modifications to the noise source itself, or to the workplace environment. To prevent adverse outcomes of noise exposure, noise levels should be reduced to acceptable levels. Annoyance, stress and interference with speech communication are the main concerns in noisy offices, schools and computer rooms. Permanent hearing loss is the main health concern. In heavy industrial and manufacturing environments, as well as other situations such as farms, cafeterias, or bars. Noise is one of the most common occupational health hazards. Why is noise an important workplace hazard? Back to top It is also very delicate: this is why loud sound may damage hearing. The hearing mechanism in the ear is sensitive enough to detect even small pressure waves. Even very loud sounds produce pressure fluctuations which are extremely small (1 in 10,000) compared to ambient air pressure (i.e., atmospheric pressure). The brain interprets the information as sound. The hearing mechanism of the ear senses the sound waves and converts them into information which it relays to the brain. Table 1Īpproximate Speed of Sound in Common Materials In gases, the higher the velocity of sound, the higher the pitch will be (Remember the 'Mickey Mouse' sound when people talk after inhaling helium gas?). Table 1 lists the approximate velocity of sound in air and other media. These pressure variations travel through the air as sound waves ( Figure 1). Thus, as the drum surface vibrates, it creates alternating regions of higher and lower air pressure. When the surface moves in the opposite direction, it creates a negative (lower) pressure by decompressing the air. This creates a positive (higher) pressure by compressing the air. As it moves forward, it pushes the air in contact with the surface. The drum surface vibrates back and forth. To illustrate, imagine striking a drum surface with a stick. These air pressure changes travel as waves through the air and produce sound. When an object vibrates, it causes slight changes in air pressure. Sound is produced by vibrating objects and reaches the listener's ears as waves in the air or other media. In either case, it can be hazardous to a person's hearing if the sound is loud and if they are exposed long and often enough. Rock music can be pleasurable sound to one person and an annoying noise to another. The difference between sound and noise depends upon the listener and the circumstances.

Why are there different decibel scales