Working with PC audio...
(Note : click on the stop button in the MIDI file player window below if music auto-starts and you prefer to stop the selection currently playing.)
Virtually every PC now comes with audio (hardware) functionality that is either integrated on the motherboard or found separately on a sound card. Your PC can be expected to play three main kinds of sound types : WAV files, MIDI files, and audio CD files.
The category of WAV sounds would primarily include your PC system sounds, like dings, chords, buzzers, etc. You control the volume of WAV sounds by controlling the WAV volume level and the master volume level in your PCs mixer. Other sound file types like MP3s use the WAV volume control as well.
Single-click on the speaker icon in the system tray to modify your PC's overall sound volume. Double-click on the same icon to get to your PC's mixer, with which you can change the settings for an individual channel and "mix" levels. (You may have to alter the preferential settings of the mixer to see controls like those shown in the image here.) Balance (Left/Right output) for individual channels can be controlled in the mixer, and individual channels can be set to mute (volume to 0) as well.
Original sounds or vibrations (of interest to us are those at frequencies with which the human audible system can resonate) can be transmitted and amplified or recorded and later played back if we apply some basic physics. To pick up the vibrations initially and move them to a replication-, an amplification- or a recording device, we use microphones - that is to say, we convert the vibrations to electrical impulses through the use of magnets and wire coils (demonstration). We can simply transmit these impulses and revert them back to equivalent vibrations at another location (as a telephone would), or we can conduct these impulses through circuitry that can alter them - in most instances to simply amplify them - for immediate reversion back to vibrations that we can hear via electromagnetic devices called speakers.
When sounds are transmitted in this way, the quality of the electronic circuitry has a lot to do with the quality of the analogous reproduced sound. While degradation is what we fear, there are some who would say that certain circuitry can actually warm up and improve reproduced sound. Typically though, we desire duplication, though this can be very hard to achieve. As an alternative to analog sound, we can convert sound to a digital format and represent the sound with a series of digits. On the way to reproduction, these digits can be immutably relayed through digital equipment which can act on the digital information without changing or degrading it, except where the digital representation is intended to be changed - to alter the original sound. The more digital equipment used, the less degradation there will be - from digital microphones on through such devices as mixers, equalizers, compressors and amplifiers, then on to digital speakers.
Sound impulses not intended for immediate reproduction can alternatively be directed to recorders that can preserve the sounds for reproduction at another time and place. Early recordings were preserved acoustically on foil-wrapped metal- or wax cylinders. Electronic recordings onto hard rubber disks followed, and were subsequently improved upon by disks made of hardened shellac that rotated at 78 RPM when played. Vinyl records (33 1/3 RPM, 45 RPM, singles, EPs and LPs) and magnetic tape (reel-to-reel, 8-track or compact cassette) improved the recording industry further. Today, digitally-recorded sound impulse information is commonly written in digital format by laser onto polycarbonate disks (CDs and DVDs). Each technological advance has meant less and less degradation of the original recorded sound.
Since records of digital information can be created and magnetically- or optically stored, we are brought back into the realm of the PC.
A WAV file is a digital record of an original recorded sound. WAV files are usually not small. A 16-bit, 44100 MZ stereo WAV file representing a three-minute song would be approximately 50 MB in size. To the ear, this would be the rough equivalent of an good audio cassette recording. WAV files can be made smaller by reducing the bit level or the frequency used, or by changing from stereo to mono. Smaller files, of course, have less information in them and will deliver less sound overall, but this may not be noticable in the PC environment.
MP3s are compressed WAV files. MP3 rippers use mathmatical algorithms called CODECs to encode WAV files and so reduce file size dramatically. An MP3 version of a three-minute song will only be from one-forth the size to one-tenth the size of the original, and will still be quite listenable. This is what makes MP3s so popular. (Worth a mention at this point is Ogg Vorbis, a new file type offering better compression and a few other improvements over other compression technologies.)
When WAV files or MP3s are played, there is a lot of processing involved. The CPU, the sound card hardware and the hard drive or CD player are all used to different degrees. The sound you hear when a high-quality WAV or MP3 file is played may be very complex or quite simple, but it will resemble the body and fullness of the real world.
An alternative type of sound file, called a MIDI file, can be an effective alternative if the sounds to be played can be satisfactorily synthesized. A modern sound card has "instruments" built into it, usually 10 of them. It can replicate the sound of drums, or piano, or trumpets or other instruments to an impressive degree. A MIDI file is more of a digital type of sound file. It has information in it pertaining to its ultimate playback: it is not an analog copy of the original sound. A MIDI file player tells the sound card when to play a given instrument's sound, how long it should be played, at what pitch it should be played and at what volume it should be played. It does not have to tell the sound card how to play the instrument. Hence, a full-sounding MIDI file can be a great deal smaller. For example, the playing of a scale on a synthesized piano might only require the passing of a couple of dozen bytes of data or so, compared to an analog recording whose file size is based primarily on the length of time it took to play the scale. The MIDI sounds are played through a separate channel of the PC's mixer so there is a separate audio channel control for it (see image above).
Here we have three examples. The first is a WAV file called notify.wav which plays the sound of "you have mail", familiar to Netscape users. It is 117 KB in size for the two notes it plays. A comparable MP3 file is only 47 KB in size, and probably could be compressed even more without losing the essence or quality of the sound. Both files play about two seconds worth of music, and both sound more or less the same. The third example here is a 67 KB MIDI file, a clasical selection by Dvorak, which sounds pretty good considering that it is synthesized. It will play for a full twelve minutes and twenty-five seconds - very efficient...
WAV :MP3 :MIDI :
Note : unfortunately, different browsers and different versions of browsers will react to these sound files in different ways. Some will play them automatically upon entering this page. Others will give you small screens from which you may play the files independently. And still others, in need of upgrading or in need of plug-ins, won't play these files at all until you either upgrade or get the necessary plug-in. So, here are links to these files through which you may open or download the files and play them on your machine with your existing sound playback software.
WAV : notify.wav
MP3 : notify.mp3
MIDI : Dvorak selection
And here are the links for upgrading your browsers, should you wish to do so. If plug-ins are required, your browser will automatically prompt and direct you to their source.
Second note : if you do not hear the sounds playing at a reasonable volume when you do play them, your sound settings need adjustment.
CD audio is something else again. The digital data on an audio CD is stored in a unique way. Instead of traditional "files", the audio data is stored in a multi-layered fashion - so audio CDs will still work for the most part even if you happen to damage areas of its surface. The data on the CD needs to be decoded or interpreted for playback or copying (ripping). A typical CD can hold about 74 minutes worth of music, or about 24 songs. For comparison, a burned CD (one created in a CD writer) can hold around 120 or so songs in high-quality MP3 format - something like 6 hours worth of music. (Again, it's no wonder MP3s are so popular.) The audio channel control for CD audio is found alongside the other channel controls in your audio mixer.
Playback for audio CDs can be controlled by Windows CD Player, or Windows Media Player, or the sound software that came with your sound card, or with a third-party program like RealAudio, Quicktime or Winamp. You can even change tracks with the rudimentary controls on the face of your CD player. This brings us to the one issue of PC audio that makes it difficult to manage - that is, the fact that there are so many places you need know about to get full use and control of sound. I have mentioned the simplest volume, balance, and muting controls in the mixer already, but most of the other software for sound that you have will also have all of these controls. (Let's not forget that your speakers may also control volume, balance and tone.) The software you use may even have additional controls (in the case of Winamp and other software) with which you can change the EQ (equalization or adjustment of the individual frequencies within the sound itself) or fade tracks in and out. It can be extremely frustrating to run from one screen to another just to get the sounds you want to record or playback when and how you want.
Playback of audio happens in "the background" of the general operation of your PC. You can quite easily carry on surfing or word processing while MIDI or CD audio files are playing without noticing any ill effects. If you try playing MP3s though, you may notice stuttering during playback when other programs try to use the hard drive. MP3s are decoded on-the-fly and use the hard drive heavily; while a certain amount of the decoded MP3 file exists in a memory buffer before it is played back, the buffer is only as deep as the amount of available RAM allocated by Windows - hence the interruptions.
In the mixer depicted above, you may have noticed two other channels - AUX and LINE IN. AUX is usually an internal jack on the sound card which can be used to accept audio output from a second CD player. LINE IN is an external port (described more fully later in this article) for accepting line level audio signals from an external sound source.
Since the sounds available for playback are each on their own channel, you can hear WAV, MIDI and CD (AUX and LINE IN) audio files played simultaneously. This can be a little disconcerting to the ear at times, and problematic if you plan to record LINE IN or CD audio with your PC while system sounds on the WAV channel are left unmuted (you will distinctly hear system sounds in your recorded files).
When your sound card was originally installed, information about its particular type and capabilities was established in the operating system (Windows). This information can readily be found under the System and Multimedia icons of the Control Panel. When opened, you will find screens similar to the ones depicted here. This is where you can ensure that your sound card is installed correctly, and where you can choose the preferred devices for playback for each of the different types of sound devices. Usually this has been all set up correctly for you when you bought your PC, but things do accidently change by themselves sometimes, or you may have a good reason to make an adjustment here.
For most PC users, the only audio functionality required is the playback of system sounds and other sound files within the confines of the PC itself. But for some, having the ability of moving sound data from their PC to an external recorder or player, or bringing sound data from an external source into their PC may be something they would like to do.
The three physical, external ports of this hardware typically are :
1) the line/speaker output
2) the line input
3) the mic input
These ports are described in the audio world as being (female) 1/8" stereo mini jacks. PC speakers and PC microphones come with mating (male) cabling.
A fourth port on older sound cards permitted the line level out and speaker out to be separated. On high-end sound cards, there may also be a second line out or some other feature.
An associated port, dating back to the addition of sound cards to much older PCs, is the joystick or game port. Users wishing to upgrade their PCs years ago would get all these ports on one expansion card. Internally, there was also an IDE or a SCSI port connector on these cards for those few users who could afford the luxury of a CDROM. (My first sound card and CDROM cost me around $750. Today, newer and better ones cost only around $100 for both the sound option and the CD player together.)
To connect to the outside audio world, you will need to look at the input and output jacks of the external devices you wish to connect to. (Note : not all eternal audio-capable devices have input and output ports.) Connecting to a "boom box" or similar mini-stereo system may only require a length of audio cable with male 1/8" stereo mini jacks at both ends. Connecting to a full-blown stereo system or to a VCR or TV will likely require an adapter cable with a male 1/8" stereo mini jack at the PC end and dual male RCA jacks at the stereo system end. Matching input ports to output ports is important: think of the audio signal as flowing - the signal must flow from the output of one device to the input of another device.
Sounds generated on a PC can be played back or recorded on external devices in the usual manner. On the external devices, you are looking for a switch or setting of some kind to select line input as the source. Sounds generated externally can be recorded on your PC with Windows Sound Recorder, with the sound software that accompanies sound hardware, or with third-party sound software like Cool Edit 2000. You will need to select and adjust the correct channel input of your sound hardware - double-click on the speaker in your system tray, and choose Options and Properties to get at the sound level settings.
Note : microphones operate in a different fashion and at a much lower level of output than all other types of audio devices. (Mic level is about one-tenth that of line level, and the cables are different as well.) Mic ports are intended to accept mic levels, and line-in ports are intended for line-level output devices. You will achieve extremely poor results if you mix the two up.
Remember that audio can be recorded at different quality levels. For instance, a three-minute song at relatively top quality will take up about 50 MB on your PC. Since 50 MB is a lot of space, you need to have enough space on the PC to save all the files generated in the process. Since the average recording software has only rudimentary start-and-stop ability, you usually need to edit the file with a sound file editor. Since you are basically editing a regular computer data file when you are doing this, you will need space for concurrent temp and transient files - or 150 MB total - which is quite a lot. Since most people have only 10-20 MB RAM available (out of the typical 64 MB RAM), the hard drive is used heavily, so you need a lot of available hard drive space. With all the writing to and from the hard drive, this is a very slow process in all but the best machines. Ideally, you need a top PC (PIII 866 MZ or higher) with 256MB RAM or more, and a deluxe sound card with deluxe editing software, if audio is serious business to you.
Remember, too, that MP3 files are compressed versions of WAV files. Unfortunately, sound file editors much decompress MP3s (in whole or in part) to work with them. When editing a 5 MB MP3 file, you wind up right back around 50 MB for the expanded three-minute 44100 MZ stereo sound file.
Software to record and play these sound files include Windows Media Player, Real Audio Player, and Winamp. Cool Edit 2000 can additionally manipulate the data - change the file type, length, and quality, combine files, separate components, etc. - and does all this very well.
Digital audio extraction...
Digital audio extraction can be described as taking an audio CD, which has digital information arranged on it in a non-linear fashion (in CDA files), and converting the data to a linear data file (an MP3 file, for example).
To learn about "ripping" your own CDs, try here... To learn about editing MP3 files, try here... To download MP3s from the Internet, see PCN's multimedia page with some tips and links to follow... To download a program that can remove ID tags from multiple MP3 files at one time, click here... To find MIDI files on the Internet, try searching for them with Google.
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