In everyday use, decibels are used to measure the volume of a sound. A decibel is a logarithmic unit to base 10, which means that if you turn the volume of a sound up to 10 decibels, that sound will be twice as loud as the "base" sound. In general terms, the decibels of a sound are obtained by means of the formula 10Log10(I / 10-12), where I is the intensity of sound in watts per square meter (w / m2).
Method 1 of 3: Decibel Chart
The table below shows the different decibel levels for common sound sources. Information on hearing damage caused by exposure to each sound level is also displayed.
|Decibels||Sound sources||Health effects|
|30||Background sound in a calm field||None|
|40||Background sound in libraries or in a quiet city||None|
|50||Relaxed conversation, normal activity on the outskirts of a city||None|
|60||Sounds in a busy office or restaurant, loud conversation||None|
|70||Television volume, sound of traffic on a highway at 50 feet (15 meters)||None; annoyance for some|
|80||Noise in a factory, processor, or car wash from 20 feet (6 meters)||Possible hearing damage after prolonged exposure|
|90||Noise from a lawnmower or motorcycle at 25 feet (7 meters)||Probable hearing damage after prolonged exposure|
|100||Outboard motor or pneumatic drill noise||Serious hearing damage after prolonged exposure|
|110||Sound at a rock concert or steel mill||Possible immediate pain; great possibility of damage after prolonged exposure|
|120||Chainsaw or thunder noise||Usually immediate pain|
|130-150||Take-off of an airplane on an aircraft carrier||Immediate hearing loss or possible ruptured eardrums|
Method 2 of 3: Measuring Decibels Using Instruments
Step 1. Use your computer
It is very easy to measure the decibels of a sound using your computer if you have the right software and equipment. Below are some ways to measure decibels with your computer. Keep in mind that the better the recording equipment, the better you will get. In other words, while your computer's internal microphone can be used for some activities, a separate, good-quality microphone will be much more accurate.
- If you're using Windows 8, download the free Decibel Reader app from the Microsoft app store. This application uses the microphone of the computer to pick up sounds of up to 96 decibels. You can get similar apps from Apple's app store, iTunes.
- You can also measure decibels with a third party program. For example, the free sound recording program, Audacity, has a simple decibel meter built in.
Step 2. Use an application on a mobile device
If you want to measure sounds instantly, mobile device applications will be very convenient. The microphone on your device can be surprisingly accurate even though it is not as good quality as the microphones you can connect to your computer. For example, mobile device meters may differ by 5 decibels from professional meters. Below you will find a short list of the applications available to measure decibels with mobile devices:
- 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 devices: Decibel Meter Free, Cyberx Decibel Meter, Decibel Meter Pro.
Step 3. Use a professional decibel meter
Although professional meters are generally expensive, they are perhaps the most direct and accurate way to measure the decibels of a sound. These instruments are also known as "sound level meters" and you can get them online or in specialized stores. Sound level meters use a sensitive microphone to measure ambient sound and give an accurate decibel value. Since there are not many stores where these instruments are sold, they are usually expensive: the cheapest models can cost as little as $ 200.
Note that sound meters or sound level meters can have other names. For example, an instrument called a "dosimeter" has basically the same functions as a sound meter
Method 3 of 3: Calculate Decibels Mathematically
Step 1. Calculate the intensity of the sound in watts per square meter
For practical purposes, decibels are considered a measure of volume. However, the truth is a bit more complex. In physics, decibels are considered a convenient way to express the intensity of a sound wave. The greater the amplitude of a sound wave, the more energy it will transmit, the more particles it will move through the air, and the more "loud" the sound will be. Thanks to the relationship between the intensity of the sound wave and its volume in decibels, it is possible to obtain a measurement in decibels knowing only the intensity level of a sound, which is generally measured in watts per square meter.
- Note that the intensity of the sounds is very low when it comes to common sounds. For example, a sound with an intensity of 5 × 10-5 (or 0.00005) w / m2 measures about 80 decibels, which is the volume of the sound from a food processor or blender.
- To better understand the relationship between intensity and decibels, pay attention to the following example. Imagine that you are a music producer and you want to know the level of background sounds in your studio to improve the sound of your recordings. After installing the equipment, you detect that the intensity of the background sound is 1×10-11 (0.00000000001) w / m2. Take this information into account in order to see in the next steps how to obtain the decibel measurement of the background sound in your studio.
Step 2. Divide by 10-12.
When you have obtained the intensity of the sound, you can express it as the formula 10Log10(I / 10-12) (where "I" is the intensity in watts per square meter) to obtain the measurement in decibels. The first step is to divide by 10-12 (0, 000000000001). 10-12 represents the intensity of a 0 decibel sound. So, if you compare the intensity obtained with this value, you will be establishing the relationship between the intensity and the decibels on the base value.
- In the example given, you will need to divide the intensity, 10-11, by 10-12 to get 10-11/10-12 =
Step 3. Take the Log10 of the result and multiply it by 10.
To finish the calculation, take the logarithm in base 10 of the result and multiply it by 10. You must do that because decibels are logarithmic units in base 10, that is, if a sound increases by 10 decibels, the intensity of the sound is doubled.
- It is very easy to solve the example. Log10(10) = 1. 1 × 10 = 10. Therefore, the background sound in your studio has a volume of 10 decibels. Although the volume is very low, the recording equipment detects it because it is of very good quality and then you will have to eliminate that sound to improve your recordings.
Step 4. Understand why decibels are logarithmic units
As you have read, decibels are logarithmic units to base 10. For any decibel, a sound that you increase by 10 more decibels is twice as loud; if you increase it 20 decibels, it is four times stronger, and so on. These values make it easier to describe the intensity of sounds that the human ear can perceive. The loudest sound the ear can hear without pain is more than a billion times louder than the lowest sound it can detect. By measuring with decibels, you avoid having to use very large numbers to describe common sounds; with decibels, only numbers with a maximum of three digits are needed.
- Think about the following: which is easier, 55 decibels or 3 × 10-7 v / m2? Both values express the same thing. So decibels allow you to use a simple value for everyday use instead of having to use scientific notation (or a very small decimal).
- Note that level 0 on a sound meter is not equal to 0 decibels. Instead, it is the level at which the sound has no distortion on the device.
- Watts (as in watts per square meter) are a physical unit for measuring energy. There are other units for measuring energy: kilowatts, milliwatts, etc. Make sure to convert those measurements into watts before using them to measure decibels by following the formula proposed in this article.