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Room Frequency Response

Dennis Foley April 23, 2014 No Comments
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One indicator of your room’s acoustic health is its frequency response. The frequency response of your room is just what the name implies. It is your room’s response to the frequencies or music you produce inside of it. Each frequency has a certain length or, technically, wavelength. A 30 Hz. wave is around 37 long. A 5,000 Hz. wavelength is around 2′. How each of these wavelengths fit into your room is reflected in your room’s frequency response. In order to understand how well each frequency fits into our room, we take a picture of its behavior in our rooms by measuring the frequency response with a device called a RTA or real time analyzer.

Measuring The Frequency Response In Your Room

A RTA has a microphone that receives the sound energy within your room and then sends that signal to software that is designed to measure frequencies in real time, thus the word real time analyzer. The data can then be displayed on a video screen such as a lap top or an external screen. There are numerous software programs available in the net. True RTA is one of those programs and I have included a link to their free software trial download. As with most things on the internet, companies will let you use the software for a trial period and give you just enough features and benefits to create the desire within you to purchase the software.

www.trueaudio.com/rta_abt1.htm

Resolution

One of the features you will find in most RTA software programs is resolution. Resolution is how the software breaks down the frequencies received at the microphone position. Most resolutions are broken down into octave bands. Octave bands, without getting too technical is the grouping of certain bands of frequencies that can then represent low, middle, and high frequencies. Octave bands are formulated around the way way we actually hear sounds due to the structure of our inner ears.

Four Main Resolutions

The resolution in most RTAs is broken down into 1/3, 1/6, 1/12, and 1/24 resolutions. These different resolutions offer different pictures or incite into how your room is handling different frequencies within the octave bands. You can think of each resolution as a magnifying glass into the frequency response expressed in octave bands. The lower the fraction size, the higher the resolution into your room’s frequency response at a chosen octave band. The most common resolution is 1/3 but for really magnifying how your room is reacting to different frequencies, 1/24 works best. You can hear individual frequency differences at 1/24 resolution.

Practice, Practice, Practice

Install the microphone at the listening position and activate the RTA in 1/3 resolution. Make sure you can comfortably view the screen while your music is playing. Take a favorite song that has an abundance of bass guitar, whether electric or acoustic. Observe how the bars in the RTA below 100 Hz. react in comparison to the other bars above. Are the bars consistently higher in this region over the other bars? Do they exceed an average level on a consistent basis? Take the middle octave range and play a vocal first male and then female. Do you see a similar “bump” in this region over the other octave bands? How about higher frequency instruments. Repeat this same procedure for them.

Patterns Will Emerge

Over time, you will start to see patterns in your room frequency response. You will notice that low frequency energy is always more dominant, no matter what the music selection you choose. You may notice that the middle octave bands are always below the low and high frequency bands. This is why it is critical to have the RTA and the video screen going at all times. It is the sonic picture of the frequencies within your room and by studying the picture, you will see where your room is deficient in some areas and exaggerated in others. We will discuss how to deal with these “high” and “low” areas using room acoustic treatment in future blogs and videos.

In Summary
I hope this explanation helped. Please leave any comments below so I can get back to you. Don’t be afraid to hit those Facebook like, Google+ and Twitter buttons on the left hand side so other people can see this post. And if you want to learn more about this subject please sign up for our free room acoustic treatment videos and ebook which provide step by step instructions. Get instant access by signing up now.

Thanks
Dennis

Dennis Foley

I am an acoustic engineer with over 30 years’ experience in the business. My technology has been used in Electric Lady Land Studios, Sony Music of New York, Cello Music and Films founded by Mark Levinson, and Saltmines Studios in Mesa, Arizona, along with hundreds of others.

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