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Recording Magazine sends out a newsletter to its subscribers every few weeks. The newsletter is (coincidentally) titled “Sound Advice” and this month it features the first in a series about room acoustics. As you will read, room acoustics is one of the biggest concerns for Recording Magazine readers. I know that this is also a big issue for those of you in the voiceover world. So, I asked permission to reprint this newsletter (and will ask to reprint the others in the series as well) so that those of you with home studios can also benefit from the information. I want to personally thank Brent Heintz, VP/Associate Publisher for granting permission, allowing me to share this great information with you.

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Here is the newsletter:

Welcome to Sound Advice on Acoustics! In a recent survey of our readership, the number one answer to the question, “What do you feel most limits the quality of your home recordings?” was “Room acoustics.” There’s a lot to learn about the subject of acoustics, and the more you know, the more tricks you can master to get your room sounding its best.

New York-based producer/engineer Joe Albano brings us the first installment of a multipart primer on acoustics to get this newsletter started, and over the coming months we’ll bring you all kinds of useful information on acoustics! Here we go…

***

We’ll start our look at acoustics by briefly reviewing the basics of how sound works.

Sound is created by vibrating objects like guitar strings, drum heads, vocal cords, or loudspeakers; it travels through the air in waves. The waves are alternating areas of higher and lower air pressure; everything we do to control the sound of a room boils down to managing what happens to those waves as they move around the room.

When we talk about a sound wave or audio signal, it has some properties that we’ll need to understand.

1. There’s its amplitude (what we perceive as “loudness”). This is measured indecibels or dB. The decibel is a relative measure of loudness, and needs a reference point to have an absolute value (we talk about 0 dB Full Scale in digital audio all the time, for example). In acoustics, we’re usually talking about dB SPL or Sound Pressure Level, from the threshold of human hearing at 0 dB SPL all the way up to very loud sounds above 100 dB SPL.

2. There’s its frequency, or how many times per second the wave compresses air; it’s measured in wave cycles per second, or Hertz (Hz). We say that the A above middle C has a frequency of 440 Hz.

3. There’s its waveshape. All sound waves are made up of a combination of basic simple waves called sine waves. There’s the lowest frequency wave, thefundamental, and then a mix of higher-frequency information blended into it calledovertones. Every sound has a different blend of overtones over time; that’s what makes a flute playing a C sound different than a horn or guitar playing the same note.

Some overtones are multiples of the fundamental—if the fundamental is at 55 Hz, there may be overtones at 110, 220, 440, etc.. These overtones are called harmonics. Other overtones are inharmonic, without this clear relationship to the fundamental. We hear them as clangorous or noisy, like the attack of a ringing bell or the chiff of breath on a flute.

4. There’s its wavelength… how long a distance you can measure between the start of one wave and the start of the next. This is a really important property, because how a sound wave “fits” into a room has a direct bearing on how loud or controllable it is!

We can calculate the wavelength of any wave if we know its frequency and its speed; this applies to light waves, sound waves, any kind of wave. The formula is simple:

Speed = Frequency times Wavelength, so Wavelength is Speed divided by Frequency.

Now, we know the speed of sound in air at sea level; it’s 1130 feet per second (fps). So a sound wave’s wavelength in feet equals 1130 fps divided by the frequency in Hz.

Here’s a couple of examples: A low E on a guitar has a fundamental frequency of 82 Hz; its wavelength is 1130 / 82 = 13.8 feet. That’s a pretty long wave. Compare that with the highest C on a piano. Its fundamental frequency is 4000 Hz, so its wavelength is 1130 / 4000 = 0.28 feet, or a bit over 3 inches: a much shorter wave.

So, as you can imagine, when we play back music on loudspeakers or have a set of instruments playing in a room, there are all kinds of waves bouncing around at all kinds of wavelengths. When two of them happen to line up so that a high pressure area of one is at the same place as another high pressure area, the overall pressure will be still higher, i.e., the wave will be louder. And when two of them line up so that a high pressure area of one is at the same place as a low pressure area of another, they’ll partly cancel out and the wave will be softer.

In other words: in any given room where there’s sound, certain frequencies will be louder than you think they’d normally be, and certain frequencies will be softer. The room won’t be accurate in representing the actual sound being played, and if you track and mix in such a room then play your music back elsewhere, it won’t sound the way you think it should. Presto: you now know why acoustics and sound control in rooms is so important!

Next time, we’ll start to look at how these properties of sound combine to create real-world acoustic problems. See you then!

Hi everyone!

I’ve been away for a couple of weeks (one of those in Italy), but I’ve returned and am looking forward to getting back to blogging and helping VO talent sound their best.

Tonight I’ll be drawing the name of the winner of a copy of SOUND ADVICE – Voiceover From an Audio Engineer’s Perspective. Today is your last chance to post a photo of your home studio setup to facebook and tag me in the photo. Thanks to everyone who entered. There are some great looking studios out there!

I’d also like to mention that there will likely be some changes coming to both my website and facebook page for the book. I’ll keep you posted.

Have a great day!

Dan

Did that headline grab your attention? Good. But please get your mind out of the gutter. What I’m referring to of course, is your voice and I’m suggesting that you use it in new ways. Let me explain…

Last night I had the pleasure of emceeing our Cub Scout Pack’s Pinewood Derby. For those of you who don’t know… the Pinewood Derby is where Cub Scouts race wooden cars that they’ve built down a long sloped track. The Pinewood Derby is one of the biggest events in cub scouting each year and it is taken very seriously (especially by the Dads). Each car is weighed-in and raced down every available lane in a series of heats to ensure fairness. The results of each heat are captured electronically with a motion detector at the finish line. By the end of the night, winners are announced for each rank as well as the overall pack winner. Most importantly, everyone gets really excited during the event and has fun.

So, how does this relate to voiceover? Simple really. As I mentioned, I emceed the event. I was not expecting to be in this role, so it was a bit of a surprise (like getting a script just as a session is supposed to begin). The Cubmaster had planned on doing it but was not feeling well, so he asked if I would.

This scenario is quite a bit different from being in a quiet room where nobody even sees me when I’m working (engineering or voicing). It got me behind the microphone in front of a large, noisy and yet still somewhat intimate crowd. Having been a live sound engineer and in radio for a number of years, my only stage experience consists of announcing bands to completely impersonal crowds of thousands or to saying “one, two, one, two” to test microphones. So… this was a very different experience for me.

I had no idea what I was going to say to keep the crowd entertained throughout the night (ugh, where’s my script?) but began by welcoming the crowd, announcing the event and just taking it from there. As the night went along, it got easier and more fun. I took on the role of an announcer, just as I would if I were in the booth reading a script. By the end of the night, several people had come up to me to say that I “missed my calling” (which I thought was kind of funny). It was fun to use my voice in a completely different way and in a completely different setting.

Versatility is a key component to success in voiceover. The more styles and deliveries you are able to successfully provide will open doors to greater and more varied opportunities. Putting yourself in different situations, such as going to another studio or on stage will give you more confidence and invaluable experience. If your current specialty is to be an announcer, practice reading as a story-teller or develop a character.

So, get out there! Try new things and use your voice (your tool) in the same way a scout uses a pocket knife… as a multi-tool.

- Dan