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For a mic level device providing -31 dBu (or 0.021Vrms) maximum output voltage to a Biamp device the correct input gain setting is +54 dB with a 'fine tuning' of +1 dB to match the level of the input. Again, since the supplied voltage has been decreased you need to increase the input sensitivity to get back to 0dB. Specifies the current volume of the audio/video. Must be a number between 0.0 and 1.0. Example values: 1.0 is highest volume (100%. This is default) 0.5 is half volume (50%) 0.0 is silent (same as mute).

1. Propervolume 1 1 3 – Audio Volume Input Output Control Levels In Blood
2. Propervolume 1 1 3 – Audio Volume Input Output Control Levels Normal Range
3. Propervolume 1 1 3 – Audio Volume Input Output Control Levels Indicate
4. Propervolume 1 1 3 – Audio Volume Input Output Control Levels Explained

Or, How to Be Certain Your Recording Is Loud Enough

An important aspect of the technical side of getting a good recording is toproperly set the volume level of the recording input. This is thelevel at which your recording device is receiving your voice while you read.You want to avoid having it being too low or too high. A level set too highresults in distorted sound. Set too low, and you often end up withtoo much noise (i.e., hiss or hum) when your recording is lateramplified to a standardized level.

In addition, this guide was originally written by a user who works onMS Windows. While some of the details are specific to MS Windows,the concepts apply generally.

• 1Adjusting the Recording Volume, Take 1
• 2Sound under MS Windows

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Adjusting the Recording Volume, Take 1

Testing

You will need to test the input volume on your recording set-up tomake certain it is neither too loud nor too soft. Make sure to test after you have changed your settings as well, to be certain your volume is at the correct level before you record.

• Start with all recording levels set to about three quarters of maximum.
• Make a short test recording of you reading as you will for a normal audio book recording.
• Set the computer's volume to about half of maximum, and play back the recording in your recording software.

Your volume needs to be adjusted further if:

• The wave forms consistently reach the highest point. This is called peaking, and will have a sound of more vibration in your voice than is normal.
• You can barely hear the recording. You should not have to strain in order to hear your voice.

If one of the two above statements is true about the test recording you've just done, then turn up or down the input volume(s) a bit and record again. Continue until you've reached the point where your volume level is just perfect. It is recommended to use headphones when playing back your test recording because it is often an accurate judge of how loud or low sound is. Also, there are many volunteers on the Forum who would be willing to lend a second set of ears to determine whether or not your test recording is at the right level.

If your recorder is something other than a computer, say, a video camera, now would be a good time to transfer your test recording to your computer for a further check of its volume level. [FIX: link]See the instructions for this process.

This is the basic approach for all methods of recording. The most common recording set-up used by !LibriVox volunteers is a computer with an external microphone, along with recording software. But otheroptions include digital audio players, video cameras and camcorders, and audio tape recorders. See [FIX: link] for details.

Peaking (Clipping)

If the volume level of the input signal (your voice) is too highduring the recording process, the loudest peaks will get clipped, thatis, chopped off. Too much clipping and the recording soundsdistorted. (This is explained in [#detailed_explanation more detail] below.)

These two screen shots show the same wave form at three differentlevels in two different programs.

• The first third of the wave form shows an input level that is too high. You can see how the peaks have been clipped, especially in the Cool Edit picture.
• The input level for the middle third of the wave is much too low.
• The last third on the right-hand side shows a recording with a good volume level.

Audacity (shows the upper portion of the wave form display):

Cool Edit 2000 (shows the lower portion of the wave form display):

Sound under MS Windows

Under MS Windows, sound levels -- for both recording and play-back --are set in several places. How you do this depends on your recordingsoftware; your PC; and, in particular, its sound card. If the soundcard is integrated into the main circuit board (i.e., the mother board),which is typical of inexpensive PCs, then you will use the 'VolumeControl' program supplied with MS Windows. This is referred to inrecording software variously as the 'System Mixer' or 'Windows Mixer'.On the other hand, if you have a separate sound card that comes withits own software for controlling it, then that software will replacethe MS Windows 'Volume Control'. You may need to read the help forthis replacement program, but the concepts will be similar to thosefor the 'Volume Control'.

The interface of the Volume Control program (illustrated below) lookslike a sound mixing board, although very simplified. Mixing boardsare used in the sound systems for musical concerts and similar events.All the mics and wired instruments on stage feed into separatechannels (i.e., inputs) in the mixing board. The board operator(often referred to as the 'sound man') uses the mixing board tobalance all the various inputs, which are individually controlled bythe volume slider on each channel, to achieve the desired mix, themost pleasing sound for the audience. In addition, the sound mixingboard has a master volume control, which sets the volume level of thefinal mix which gets sent to the loud speakers.

The Volume Control program works similarly, although people rarelyhave something playing in more than one channel at the same time.(But that doesn't mean it isn't possible. For example, you could playback the !LibriVox recording you're working on at the same time youplay a music CD in the CD-ROM drive, as a musical background to yourreading. You would use the volume slider on the 'CD Player' channelto set the music to a low level so it doesn't overpower your voice.)Keep in mind that the Volume Control program sets only playbackvolumes, not those for recording (we'll be getting to that presently).

As you may be beginning to see, there are several places in thepathway between source (e.g., sound file or audio CD) and speakerswhere the volume can be independently controlled. If any one of themis set to zero, you won't hear a thing. Those places are the channelvolume slider, the master volume slider (the left-most channel,labeled 'Volume Control'), and the physical volume control knob on thespeakers. A possible fourth place is the volume control of the playersoftware, but in many cases that actually remotely operates one of thesliders in the Volume Control program, usually the master control.

Since Volume Control is a program, it's configurable. You can choosewhich channels are shown on this software mixing board. To do this,open the Properties dialog:

Options [menu] >

Properties

With the Properties dialog open, notice the list under 'Show thefollowing volume controls:'. Check those you want to see in VolumeControl; uncheck those you don't.

Notice also the section labeled 'Adjust volume for:'. Volume Controlcontains a twin program, Recording Control (illustrated below). Itlooks like Volume Control in that it has multiple channel, but it'snot a mixer since you can only select one source at a time forrecording. To switch to this twin, in the Properties dialog (seeabove), select 'Recording' under 'Adjust volume for:'. In the listunder 'Show the following volume controls:', make certain Microphoneis checked if you plug your recording mic into the mic jack on yourPC. Click the 'OK' button. The program window is now titledRecording Control. If you are using the mic jack to record, thencheck the Select box at the bottom of the Microphone channel. Tostart testing your recording set-up, move the Volume slider to thetop; this is maximum volume. Your recording software likely has itsown volume control for setting the level of the signal (your voice)that it records.

If the input signal is too hot in your test recording, that is, if thesignal is getting clipped ([#clipping see above]), first try reducing the levelusing the volume control in the recording program. If that doesn'twork well enough, then return to the Recording Control program andreduce the Volume level in the Microphone channel to aboutthree-quarters of maximum. Now make another test recording.

An important concept (which it took this writer some time to absorb)is that the volume levels for playback and those for recording arecontrolled separately. What that means is that you can, say, have theplayback volume set to zero, so you can't hear anything that'splaying, but still be able to record successfully if the recordingvolume level is up. Conversely, just because you can hear somethingplaying on your PC, say a music file, that doesn't mean that thevolume level for recording is set correctly, since it might be atzero. A specific example, relevant to recording for !LibriVox, isthat you can have the Microphone channel on Volume Control muted butstill be able to record if the Microphone channel is selected and thevolume control is up on Recording Control.

Accessing MS Windows 'Volume Control'

There are several ways to open the system mixer (under Windows XP;earlier versions will differ to some degree):

• Double-click on the small speaker icon if you see it in the system tray of the task bar (which is usually at the bottom of the screen). (The speaker icon pops up a yellow tool-tip with the word 'Volume' when you mouse over the icon.)

• Alternatively, you can right-click on the speaker icon and pick 'Open Volume Control'.

Propervolume 1 1 3 – Audio Volume Input Output Control Levels In Blood

• If you don't see the speaker icon in the system tray:
  • Start [button on the task bar] > All Programs > Accessories > Entertainment > Volume Control.
• To add the speaker icon to your task bar:
  • Start [button on the task bar] > Control Panel > Sounds and Audio Devices > Volume [tab] > [check] Place volume icon in the taskbar.
• Some recording and editing programs let you open the system mixer from one of the recording program's own menus. For example,
  • Total Recorder: Options > System Mixer...
  • Cool Edit 2000: Options > Windows Mixer...

The Program Interfaces

Sound with Realtek audio

A user reports that Realtek Audio may override normal windows controls, not allowing normal volume control.

If you have Realtek audio on your computer and have low microphone volume, try this:

Open Sound Manager and then open the Mixer tab. (Not the Mic tab. Doesn't make sense but that is where they hid it). There will be a Mic volume slider bar and at the bottom two little dots. Clicking on these dots allows you to choose to enable the boost that makes a wonderful 20db difference in mike output.

Propervolume 1 1 3 – Audio Volume Input Output Control Levels Normal Range

N.B. Different versions of Realtek software vary.

Specific Software

On MS Windows

Some recording programs let you directly select the microphone channelfor input and set the volume level for that input, without having touse the system mixer. Audacity and Total Recorder are two suchprograms. For example, if you have Audacity and the Windows RecordingControl open at the same time, you can operate the input volume levelslider in either window and see the corresponding slider move in theother. That means there's no need to open the Recording Control sinceyou have control of its functions from within Audacity. The same istrue for Total Recorder.

On Linux

Increasing input volume using Linux ALSA:

$ uname -aLinux kitchawank 3.2.1-gentoo-r2 #3 SMP PREEMPT Thu Feb 23 18:32:37 EST 2012 i686 Intel(R) Pentium(R) 4 CPU 2.80GHz GenuineIntel GNU/Linux

$ arecord --list-devices# find USB mic capture device

**** List of CAPTURE Hardware Devices ****card 0: Intel [HDA Intel], device 0: ALC880 Analog [ALC880 Analog] Subdevices: 1/1 Subdevice #0: subdevice #0card 0: Intel [HDA Intel], device 2: ALC880 Analog [ALC880 Analog] Subdevices: 2/2 Subdevice #0: subdevice #0 Subdevice #1: subdevice #1

card 1: Snowball [Blue Snowball], device 0: USB Audio [USB Audio] Subdevices: 1/1 Subdevice #0: subdevice #0

$ alsamixer -c 1# set input level on card 1, the USB mic. When alsamixer opens press<F4>

A More Detailed Explanation of Recording

Let's explore this a bit more.

Part of getting a good recording is to set the volume level properly.You want to avoid having it too low or two high. A level set too highresults in distorted sound. Set too low, and you often end up with anoisy recording when the recording is amplified to a standardizedlevel. Let's explore this a bit more.

Any recording set-up has a maximum volume level which it can acceptand record without distortion. If the input level exceeds this limit,then the peaks of the sound wave which are greater than this maximumare chopped off flat at the maximum level. This is referred to as'clipping'. The more peaks that get clipped, the more the effect willbe audible. The result is distorted sound. Badly distorted sound isunpleasant to listen to. An occasional clipped peak is usually notdetectable. Therefore, you want the input level low enough so thatclipping never occurs. We'll get to how to do that in a moment.

First, though, we'll cover the opposite problem: The input level istoo low. Any audio system which involves analog signals, such as themicrophone you're using to record, unavoidably produces a certainamount of noise, often in the form of hiss (the better your equipment,the less noise it will produce). Other problems in analog systems canproduce hum, such as electrical transforms and power supplies. Thecable from your microphone to your PC can pick up electricalinterference. Unless your equipment is very good -- which means veryexpensive, your recordings are likely to have trace (or louder)amounts of hiss or hum. Fortunately, for most of these sources ofnoise, they do not increase significantly as you increase the inputlevel from the microphone. One exception is any interference beingpicked up by the microphone's cable. The higher the input volumelevel is set, the greater is the ratio between it and the noise level.This is known as the signal-to-noise ratio. Your goal is to have thisas high as possible ... just as long as your signal is not gettingclipped. But if your input signal level is much too low, then thelevel of the noise will be relatively high compared to the signal (ie,your voice). The problem here is that when the recording's level isadjusted to a standardize level, the noise gets amplified a lot, alongwith the signal. If the ratio of signal to noise is high to startwith -- that is, your voice is much louder than the noise, the signalwon't need to be amplified so much, if at all, to bring it to thestandard level. Therefore, the noise won't get amplified very much,either.

Noise removal works better the higher the signal-to-noise ratio.

So, as you may be figuring out, there is an optimum range for theinput volume level. Let's see how to do that.

From this point on, some of these instructions apply to MS Windows.

But first, a short digression. Much of the audio world thinks aboutaudio and its volume in a unit called decibels, which is abbreviateddB. Decibels are a logarithmic scale, which is used becausethat's how human hearing works. It's logarithmic, not linear. Thatis, a sound which is twice as loud as another as measured by a meterusing a a linear scale, sounds much less than twice as loud to thehuman ear. In fact, to be perceived as twice as loud, the sound hasto have ten times the amount of power; that is, it's 10 dB louder.

Most software either displays volume levels only in dB or dB units areone of the choices. It is recommended you set your recording programto display units in dB. These instructions assume that. Yoursoftware also should have a level meter. In most programs, this is abar, often horizontal, which increases in length from the left as thesound level increases. If there is no input signal at all, the lengthof the bar will be zero, but that is most unlikely, since almostcertainly your set-up will be making noise, as described above. Someaudio software let you change the scale of the level meter. Somethingclose to 60 dB is good. That is, you will have -60 dB at the left endof the scale and 0 dB at the right.

This brings us to an odd aspect of the dB scale on the level meter. 0dB is on the right-hand end of the scale because 0 dB is the maximuminput level that doesn't clip, as described above. Sounds that arequieter are shown in negative dB. This is referred to as attenuation.The larger the negative dB level (the farther to the left the meterbar is), the quieter the signal.

[Holding]

This guide contains two parts, although it's difficult to separatethem completely. One deals with how to set the volume. The other,and longer, explains why this is important.

In use, while you are recording, you will see the bar in the levelmeter jumping back and forth in response to your voice.

Some software will let you monitor the input signal level -- thevolume of your voice -- without actually recording. This lets youtest the volume setting to get it right.

Propervolume 1 1 3 – Audio Volume Input Output Control Levels Indicate

Ideally, the level should never go above, get louder than, -1 dB. Atleast one recording program marks the -1 dB lines by using thickerlines. For safety, it's better to stay below -6 to -3 dB.

If you test and see that the level of your reading is below yoursafety limit, but when you starting recording for real, you may getexcited at some point in what you're reading and talk somewhat louder.

On some programs, the bar of level meter changes color as it moves.Typically, it's green at lower input levels, indicating 'safe'. As itapproaches 0 dB, it turns first yellow or orange and finally red. Younever want to see red and only occasional see orange or yellow.

Cool Edit 2000 and Cool Edit Pro before version 2.0 used a level barthat was red at all levels.

As mentioned already, there is a happy medium for where to set thevolume level on your recorder. Unfortunately, there's noone-size-fits-all answer to what that level ought to be in terms ofnumbers or positions. So we can't tell you something simple like 'setthe input(s) controls to 45% and you'll never have to touch them againbecause that will give you perfect recordings'. The reasons includethe wide variety of types of equipment

Propervolume 1 1 3 – Audio Volume Input Output Control Levels Explained

[to be continued]