What Are Decibels (dB) in Home Theater Audio? GA S REGULAR Menu Lifewire Tech for Humans Newsletter! Search Close GO Home Theater & Entertainment > Audio 32 32 people found this article helpful

What Are Decibels (dB) in Home Theater Audio?

The decibel scale and why it's important

By Robert Silva Robert Silva Writer San Diego State University Robert Silva has extensive experience in consumer electronics and home theater product sales and sales supervision; he has written about audio, video, and home theater topics since 1998. Robert has articles published on HBO.com and Dishinfo.com plus has made appearances on the YouTube series Home Theater Geeks. lifewire's editorial guidelines Updated on August 19, 2021 Tweet Share Email Tweet Share Email

In This Article

Expand Jump to a Section What Is a Decibel? The Decibel Scale How the Scale Is Applied How to Measure Decibels Measuring Without a Meter Decibels (dB) are a unit for measuring sound. Since sound reproduction is critical for the home theater experience, it's important to understand the meaning of decibels when it comes to music. Decibels are also used to measure the power of electrical signals. This article pertains to the measurement of sound.

What Is a Decibel dB in Music

A decibel, designated by the letters dB, is a logarithmic scale of loudness. Our ears detect changes in volume in a non-linear fashion. Sound loudness—which is not necessarily the same thing as volume—is determined by a variety of factors. These include the amount of air that reaches the ear and the distance between our ears and a sound source. RonPeigl / Getty Images

The Decibel Scale

The decibel scale was created to quantify how loud sounds are. A difference of 1 dB is perceived as a minimum change in volume. A difference of 3 dB is a moderate change, and a difference of 10 dB is perceived by the listener as a doubling of volume. The threshold of hearing is 0 dB. Here are some examples of common sounds and where they typically fall on the decibel scale: Whisper: 15 to 25 dBBackground noise: 35 dBNormal home or office background: 40 to 60 dBNormal speaking voice: 65 to 70 dBOrchestral climax: 105 dBLive rock music: 120 dB+Pain threshold: 130 dBJet aircraft: 140 to 180 dB

How the Decibel Scale Is Applied

For amplifiers, decibels are a measurement of how much power it takes to produce a specific sound output level. For one amplifier or receiver to be twice as loud as another, you need 10 times more wattage output, so a receiver with 100 WPC is capable of twice the volume level of a 10 WPC amp. A receiver with 100 WPC needs to be 1,000 WPC to be twice as loud. Decibels are also used in relation to the sound output of loudspeakers and subwoofers at specific frequencies and volume levels. A speaker may have the ability to output a frequency range of 20 Hz to 20 kHz, but at frequencies lower than 80 Hz, the sound output level (volume) may be -3 dB less. This is because more power output is required at lower frequencies to produce the same volume level. The dB scale is applied to the sound level output capability of a specific speaker when fed a tone carried by one watt of power. A speaker that can produce 90 dB or higher sound output when fed a one-watt audio signal is considered to have good speaker sensitivity. For video projectors, the decibel scale is used to measure how much sound is produced by the cooling fan. A video projector with a fan noise rating of 20 dB or less is considered very quiet.

How to Measure Decibels

One way that decibels can be measured is with a portable sound meter. There are also sound meter apps that work with the microphone in a typical smartphone. Most home theater receivers have built-in test tone generators that you can use to determine the generated decibel level for each speaker. When all your speakers register the same decibel level at a given volume level, your sound listening experience will be balanced.

Measuring Decibels Without a Sound Meter

Many home theater receivers have an automatic speaker/room correction system that doesn't require the use of a separate sound meter. A microphone is provided that plugs into the front of the receiver. The receiver sends out test tones to each speaker, which are picked up by the microphone and sent back to the receiver. The receiver then determines how many speakers there are, the distance of each speaker from the listening position, and the size of each speaker. Using that information, it calculates the optimum speaker level relationship between the speakers (and subwoofer) along with the best crossover point between the speakers and the subwoofer. Was this page helpful? Thanks for letting us know! Get the Latest Tech News Delivered Every Day Subscribe Tell us why! Other Not enough details Hard to understand Submit More from Lifewire How to Install and Set Up a Home Theater Receiver Understanding Amplifier Power Output Specifications What Is Speaker Sensitivity and What Does It Mean? 5 Things to Consider Before Buying Stereo Speakers Why You Need a Center Channel Speaker What Bass Management Is and How It Works The Complete Guide to Home Audio Systems for Beginners How to Set Up a Home Theater System How Decibels and Watts Affect Loudness and Power How to Connect a Subwoofer to a Receiver or Amplifier The Difference Between Home Theater and Stereo Receivers How to Make Wired Speakers Wireless How Do I Position Loudspeakers for My Home Theater System? Tips to Set Up and Get the Most From a Sound Bar How to Turn Off Headphone Safety on iPhone How to Stop Echoes in Voice Calls Newsletter Sign Up Newsletter Sign Up Newsletter Sign Up Newsletter Sign Up Newsletter Sign Up By clicking “Accept All Cookies”, you agree to the storing of cookies on your device to enhance site navigation, analyze site usage, and assist in our marketing efforts. Cookies Settings Accept All Cookies