Want to find out? Okay, hotshot Sharpen a number-two pencil and let's go. The sound of your sweetie whispering sweet nothings in your ear is 20 dB. The sound of your mother-in-law yelling at you is 60 dB.
How many times louder is your mother-in-law than your paramour? As you're waiting in the interminably long line to get out of the parking lot after the show, you crank their latest CD on the car stereo at a level of dB. How many car stereos played at the same volume would it take to produce the same SPL as the concert?
There are two sound sources in a room: say, a drummer playing at 72 dB, and a guitar player playing at 66 dB. What is the loudness of the two playing together? Hint: It's not 14 dB. What's the dynamic range of bit digital audio in dB? Of bit digital audio? Could you figure out the dynamic range of a bit digital audio system? How much louder is a watt guitar amp than a 50 watt guitar amp?
If you can answer these questions with ease, then this article wasn't written for you. But, if you found yourself scratching your head and saying "huh? Beware the road signs that read "Caution -- Math Ahead! If you are one of those people whose eyes glaze over when faced with a pageful of equations, fear not. I'm right here beside you! Stick with it, reread it a couple of times if you have to, and before too long the light bulb will come on, I promise you.
Oh, and one more thing -- if you want to follow along with your own calculator, make sure you have a scientifical-type one that has a "log" function.
Be careful not to get the "log" button the function that computes the base-ten logarithm confused with the "ln" button the function that computes the natural logarithm, which is a kind of a log that marches to a whole different rhythm.
And so, come with me now if you will, as we step through the looking glass into the Wonderful World of the Decibel -- where subtraction is division, rulers are longer on one end than the other, and nothing is as it seems Logarithmic Scales -- the Kind You Can't Play on a Piano The term dB has meaning in all kinds of scientific measurement -- from sound, to electrical or mechanical power, to voltage, and so on.
The decibel scale is an example of a logarithmic scale. Other examples of logarithmic scales used in scientific measurement are the Richter scale used to denote the energy of earthquakes and the pH scale used to indicate the concentration of hydrogen ions in a solution. Why do scientists use logarithmic scales? Well, one thing you have to remember is that scientists -- much like guitar players -- like things easy! And when you're dealing with a large range of numbers that have a bunch of zeros before or after the decimal point, using logarithms makes those numbers a whole lot easier to work with and compare to each other.
Let me give you an example. Let's say you're a scientist in the way-back old days. You're observing some phenomena dealing with sound. You've performed a few experiments, and have taken some measurements about the intensity of sound. Okay, so far, so good Now suppose, if you will, that you've found that the smallest sound intensity that most people can hear is.
Of course, you've taken a bunch of measurements in between as well, like. Just try conveniently comparing those numbers! Quick -- what's the difference between. Try figuring that one out in your head! Let's see if we can make these numbers smaller and easier to work with. Instead of using these unwieldy numbers in their raw form, let's try taking the base-ten logarithm of these numbers, and working with those results instead.
It just so happens that: log. We can easily see here that the difference in the logarithms of these wacky figures, is an easy-to-handle "2. What are we going to call this "difference" number? You suddenly come up with a brilliant idea -- you'll call it a Bel, after your boyhood hero, Alexander Graham Bell! Alexander Graham Bell was your boyhood hero, wasn't he?
Come on, work with me here, people There is also a great deal of confusion in the vocabulary for field strength also called field intensity. Each unit has both merit and common usage in certain disciplines in the radio communications industry.
However, the widespread confusion about how they relate to one another causes both frustration and misunderstandings about system design and actual performance. The following terms will be discussed at length. The electric field intensity unit dBu is the unit used extensively by the Federal Communications Commission when referring to field strength. Electric field intensity is independent of frequency, receiving antenna gain, receiving antenna impedance and receiving transmission line loss.
Therefore, this measure can be used as an absolute measure for describing service areas and comparing different transmitting facilities independent of the many variables introduced by different receiver configurations.
When a path has unobstructed line of sight and no obstructions fall within 0. Although calculations of electric field strength are independent of the receiver characteristics mentioned above, predictions of voltage and received power supplied to the input of a receiver must carefully take each of these factors into account.
Correlation between electric field strength and voltage applied to the receiver input is impossible unless all of the above listed information is known and considered in the system design. When the exact same conditions path, frequency, effective radiated power, etc. Field strength as a function of received voltage, receiving antenna gain and frequency when applied to an antenna whose impedance is 50 ohms can be expressed as:.
There is also a fixed loss in the receiving antenna transmission line — often assumed to be lossless. To determine the level of field strength necessary to adequately receive a transmitted signal, use Equation 6 above, taking into account the frequency, receiving antenna gain and required level of receiver voltage for the desired level of quieting in the receiver.
These predictions are for the voltage at the antenna terminals. In this case, the formula is referenced to 1 milliwatt in the denominator, and the unit is dBm. When we take the logarithm, the exponent comes around into the coefficient, making our voltage formula 20 log.
In the voltage scenario, the reference value becomes 0. As with analog amplifiers, most digital amplifiers will provide an attenuation control, allowing you to reduce the signal level being fed into the amplifier - either via a front panel interface or software interface.
This is a line level control, located post-input, before the amplifier stage. The attenuation controls will have a range of minus infinity to 0dB. The amplifier may also have an amplifier gain setting. Higher amplifier gain equals higher input sensitivity, meaning a lower input level is required to reach maximum output power.
Amp gain primarily affects the amount of headroom for the system. Adjusting gain sensitivity should be utilized to optimize the ratio of amplifier headroom to noise floor. At higher gain settings higher sensitivity , more of the noise floor will be amplified and the available headroom before clipping will be lower.
In configuring an amp for the digital input, refer to its manual to find the optimal setting for your amplifier. In the example shown above, further reading of the manual reveals that for a Dante digital input the amplifier's attenuation level should be 0dB and the amp gain setting should be 35dB. Output level adjustments on the EXPO 8-channel, single full rack space are made via analog attenuation pots on the front panel of the device. A small flathead screwdriver is the tool required.
It is a variable output, there are no detente positions between the two limits. Set the next device to its lowest input sensitivity, normally 0dB or line level on the input and ensure phantom power is disabled , then connect the EXPO output to the input of the next device.
Observe the input meter of the device: if the meter is above 0dB use the attenuation pot on the EXPO to reduce the signal to 0dB on the input meter of the new device; if the meter is below 0dB increase the input sensitivity of the new device to raise the input signal to 0dB.
Recall that 0dBFS is the maximum possible setting, anything higher would be into digital clipping. These are all dBu values. There is a 24dB offset due to the different scales being used.
When connected to the Biamp Tesira a signal registering dB on the Yamaha's output meters will register as 0dB on the Biamp's input meters. The meter's reference point is different in each product. The actual level with respect to the digital clipping point of both products is the same.
This is the correct level. It shows that there is 24dB of headroom remaining before the digital signal clips. Analog output settings Note - to see the controls mentioned here in Audia or Nexia software, be sure to enable Output Attenuation when creating the Output block. The dBu setting provides a mic level signal from the output.
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