In common usage, decibels are used to measure the volume (loudness level) of a sound. Decibels are a logarithmic unit of base ten, which means that increasing the volume by ten decibels produces sound that is twice as loud as the base sound. In general, the intensity of a sound expressed in decibels is calculated using the following formula: 10Log10(I / 10-12), where I is the sound intensity in watts / square meter.
Method 1 of 3: Comparative table of noise in decibels
In the following table, increasing values of intensities in decibels are compared with common sources of noise which can generate these intensities. Information on the hearing damage that these sound powers can cause is given as information below.
|30||Sound from the distant neighborhood||No|
|40||Distant city sounds||No|
|50||Suburban activities, conversation||No|
|60||Lively restaurant, loud conversation||No|
|70||TV, highway 15 meters away||None, unpleasant for some people|
|80||Car wash at 6 m, factory noise||Possible damage with long exposure|
|90||7 m motorbike, lawn mower||Very possible damage with long exposure|
|100||Jackhammer, boat engine||Strong damage possible with long exposure|
|110||Loud rock concert||Immediate pain possible, damage with long exposure|
|120||Tonerre, electric saw||Usually painful immediately|
|130-150||Airplane taking off from an aircraft carrier||Immediate hearing loss or probable hearing membrane rupture|
Method 2 of 3: Use instruments to measure decibels
Step 1. Use your computer
With the right program, it is not difficult to measure sound intensities in decibels via your computer. Those listed below are only part of the software available. Note that the quality of the result depends on the quality of your recording material. Clearly, the microphone built into your computer is fine for some tasks, but a high-quality external microphone will be more precise.
- If you are working under Windows 8, try downloading the free "Decibel Reader" application available on the Windows online store. This application uses your computer's microphone to measure sounds up to 96 decibels. Similar products are also available through the iTunes app for Apple line products.
- You can also use a third-party program to measure decibels. "Audacity", for example, is a free recording program that includes a system for measuring sound in decibels.
Step 2. Use a laptop app
Mobile phone apps are very handy for measuring sound intensities anywhere and quickly. While your phone's microphone is probably not a high-quality microphone, it can still perform very well. For example, it is not uncommon for mobile phone applications to give a response that is in a range of 5 decibels around the value given by a professional microphone. Below is a short list of applications available for common operating systems.
- For Apple devices: "Decibel 10th", "Decibel Meter Pro", "dB Meter", "Sound Level Meter".
- For Android devices: "Sound Meter", "Decibel Meter", "Noise Meter", "deciBel".
- For Windows laptops: "Decibel Meter Free", "Cyberx Decibel Meter", "Decibel Meter Pro".
Step 3. Use a professional decibelmeter
Its price is not to be neglected, but is up to its precision. This is the most accurate way to find the intensity of a sound. Also called a sound level meter, this particular tool (available online on specialized sites) uses a very sensitive microphone to measure the amount of noise present in its environment and tells you a value in decibels. As the market for this type of instrument is quite small, their price can be quite high, count around 160 € for a low-end model.
Note that the sound level meter or decibelmeter can still have other names. For example, tools called "audiometers" have roughly the same properties
Method 3 of 3: juggle the units
Step 1. Measure the intensity of your sound in watts per square meter
For common applications, decibels are used to measure the "strength" of a sound. In physics, decibels are a practical way of expressing the noise level of a sound, its intensity (expressed basically in watts / square meter). The greater the amplitude of a sound wave, the more energy it carries and the more it moves the air particles located in its path, so the sound is more intense. Thanks to this relationship between the intensity of a sound wave and its volume in decibels, it is possible to find a value in decibels simply by knowing the intensity of the sound expressed in W / m².
- Note that sound intensities are generally low enough for everyday sounds. For example, a sound with an intensity of 5 × 10-5 (or 0, 00005) W / m² corresponds to approximately 80 decibels, which is the noise emitted by a kitchen blender.
- To better understand the relationship between measured intensity and decibel values, consider the following example. For the purposes of this example, let's say we're producers and we're trying to measure the background noise in our recording studio to improve the quality of our work. After installing our instruments, we detect background noise with an intensity of 1 × 10-11 (0.00000000001) W / m². In the following steps, we will convert this value to decibels.
Step 2. Divide this value by 10-12.
Once you find the intensity of your sound, you can simply replace it with its value in the following formula to find its value in decibels: 10Log10(I / 10-12) (where "I" represents the sound intensity in W / m²). To start, divide the measured value by 10-12 (0, 000000000001). 10-12 is the intensity of a sound of 0 decibels, so by comparing our value to this benchmark, we can get a value in decibels.
- In our example, let's divide our measured intensity, 10-11, by 10-12 to get 10-11/10-12 =
Step 3. Take the Log10 of your answer and multiply the value obtained by 10.
To finish the calculation, all you need to do is take the base 10 logarithm of your answer and multiply the resulting value by 10. This step takes into account that decibels are a base 10 logarithmic scale, which means that 'an increase of 10 decibels doubles the power of your sound.
- Our example is easy to solve. Log10(10) = 1. 1 times 10 = 10. Therefore, the background noise of our studio is 10 decibels. It is little, but nonetheless detectable by recording equipment. So we will probably need to eliminate the source of this noise in order to have good recording quality.
Step 4. Understand the meaning of the logarithmic scale
As said above, decibels are counted on a base 10 logarithmic scale. For any sound intensity value given in decibels, we know that a sound 10 decibels louder will appear twice as intense, a sound 20 decibels louder. will appear 4 times more intense, etc. This makes it possible to perceive the very wide range of sounds that the human ear can perceive. The loudest sound we can hear without feeling pain is over a billion times louder than the smallest whisper we can make out. By using decibels we can avoid the use of numbers with a lot of digits to measure everyday noises. Only three digits are sufficient with the logarithmic scale.
- In view of the above, which is easier to use: 55 decibels or 10-7 watts per square meter? The two are the same, but decibels avoid scientific notation and are more practical in everyday life.
- Note that the zero level of a sound level meter is not the same as the absolute value "0 dB". This is only the loudness at which the sound is not distorted by the device.
- Watts (as in "watts per square meter") is a unit of power. There are different variations of this unit: kilowatts, milliwatts, etc. Be sure to convert these values to watts when using the decibel conversion formula.