Decibel meter decibel scale3/29/2024 One of the decibel scales for sound provides a way of creating a logarithmic scale relative to a pressure amplitude reference. The scales vary depending on what quantity is being used as a reference. There are decibel scales defined for use in electronics and optics. The size of these increases and decreases is also related to the loudness of the sound.ĭecibel scales can be used for many measurements other than sound where there are large ranges of values. The size of these increases and decreases are called pressure amplitude. To understand the relation between pressure amplitude and decibels it helps to understand that as a sound wave moves through the air, slight increases and decreases of the background air pressure occur. It is easier and takes less room to write 0 dB or 120 dB than a number followed by six zeroes! The pressure change experienced by the ear when subjected to a 120 decibel sound ( Caution! This is the pain threshold for the average human ear!) is about one million times greater than the pressure change created by the softest sound we can hear, defined as 0 decibels. This helps us to compress the huge range of hearing so that our response to variations in loud sounds is similar to the response to variations in weak sounds. This is why the decibel scale is related logarithmically to the huge range of pressure amplitudes that the ear is subjected to. Because of this, the scale for measuring sound must also span an enormous range yet still be easy and compact to write. The ability of a normal, healthy human ear to hear spans an enormous range. If you answered YES to any of these questions, you may have been exposed to damaging sound levels When you are listening to stereo headphones or a personal music player, can a person standing next to you hear it too? (When you are using a personal music player, you should be able to understand a person next to you speaking in a normal tone of voice.) Questions to determine whether you are being exposed to excessive sound that may damage your hearing.Īre you often in an environment where the sound is so loud that you have to shout to make yourself understood?Īfter exposure to loud sound, have you ever noticed tinnitus (ringing or other noises in your ears or head)?ĭoes music sound slightly strange or distorted after you have been listening for a while?ĭo voices sound muffled after you’ve been around loud music or other loud sounds for an extended time?Īfter exposure to loud sounds do your ears sometimes feel “full” or “stopped up”? Walk away (put as much distance as possible between your ears and the sound source).Fortunately, there are several actions a person can take to prevent noise-induced hearing loss.įollowing are three major ways to obtain hearing protection: It makes no difference whether you like the loud sounds or not – if they are over 85 dB, they can begin to damage hair cells in your inner ear.īecause there is currently no treatment to repair hair cells that have been damaged by loud sound, it is important for people to protect themselves from such damage. Loud sounds (above 85 dB for 8 or more hours) can hurt your ears by damaging the sensitive hair cells of the inner ear. Noise is not the only cause of hearing loss, but it is the most common cause in America (and in other industrialized nations). Was the change faster or slower than they thought it might be?Īsk students to give examples of some loud sounds they are exposed to in their environment. Possible responses are in italics.Īsk students if the sound level changed with distance as they had predicted. Note: the results will vary depending on the acoustic characteristics of the room.Īsk students the questions in bold. Procedure may be repeated with the weighting adjustment selected for C-weighting. Collected data can be graphed with distance as the independent variable (x-axis) and sound level as the dependent variable (y-axis).Have the student move back another 10 steps holding the sound level meter and record sound levels in dB. You may need to reduce the decibel range of the sound level meter as it is moved further away from the source of the sound. Without changing the speed of blender or volume on the radio, have the student move away about 4 or 5 steps from the sound source holding the sound level meter and record the sound level in dB.This will be the initial sound level and the zero distance for comparing sound levels change with distance. Adjust the speed of the blender or volume of the radio to get as close to a steady 80 dB reading as possible.Have a student hold the sound level meter (phone or computer microphone) about 4 inches away from the radio or blender.If using a blender, turn it onto the loudest setting If using a radio, turn on the radio and de-tune near a known radio station until there is a constant static sound. Place blender or radio near the edge of a flat surface facing the classroom.
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