Sound Basics

CLICK HERE to go back

What is Sound?

Why record sound 'digitally'

Digital voice recorders have several advantages over tape recorders especially as they are now so inexpensive (start around $30 USA). The best is that they download the sound file easily to a PC via a USB link where it can be manipulated using editing software.   More sophisticated digital sound recorders are also available but move the price range up considerably. This is very useful as you may record say an hours worth of chatter and then just five seconds of something interesting comes along in the middle, so you need to cut out about thirty minutes either side. That is the very minimum you would do with an editor but there’s a bunch more that is useful making a sound editor a vital tool. Here are just some of the things you might want to do with your sound editor.

Move lumps of sound around (Cut and paste) Change the order or repeat sounds Adjust the volume or tone for best clarity Slow down or speed up the recording to analyse details Save the final version in a smaller (compressed) file size suitable for the web.

The good news is that sound editing programs can be downloaded for free and there is a recommendation below LINK on a good one to use. There are several others all with the similar feature but we will standardise on one called Wavepad from NCH. www.nch.com.au/wavepad .

A popular alternative that you may have experience with could be Audacity from Soundforge at http://audacity.sourceforge.net/ but it does not handle 'wma'* files and its 'mp3'* encoder is less versatile. (*see next)

You might wonder why such useful software is free; well some companies sell the same product with more features and wet your appetite by giving away a simpler version. This is handy as the features we need are all in the simple free one but if you start playing with some of the more advanced features a message requesting you to buy the full version will pop up.

Sound file types

Now unlike old fashioned tape recorders the digital recorder records sound as a series of numbers – a lot of numbers and they stores these as a file on the recorder itself in a silicon memory chip. This translation from sound to numbers is called Encoding. When the ‘file’ is replayed the numbers are read back by a microprocessor and translated back into the original sound. This is called decoding.

Just to make life seem difficult there several methods that can be used to Encode & Decode sound files. Some methods create very small files and some better quality.

Your recorder will usually have only one such method and therefore create only one type of sound file. The three most popular types are known as ‘wav’, ‘mp3’ or ‘wma’.

CAUTION TECHIE BIT - Try not to skip, just get a coffee, it's not so hard.

The method used to encode sound files into numbers requires the computer to know the rules of the method. These rules are stored on your computer as a thing called a CODEC standing for enCODing and DECoding. Fortunately all the popular CODECs will be on your PC already. Or to be more accurate the DECoding half will be there, so the computer will play your sounds just fine and the CODing bit to allow you to create different types is part of the sound editor when we get around to installing it. It should be clear now that your little digital recorder has within it, both an Encoder used when recording AND a Decoder used when playing back. So how does you computer know what rules (CODEC) to use to play your recorded file? Fortunately the file that was created by the recorder has a hidden part in its name that tells the computer what rules to use to decode it back into sound. The actual files created within the voice recorder will have unfriendly names, usually a number say A000123.mp3, A000124.mp3, A000125.mp3 where mp3 is just the specific type of sound file. Depending on how your computer is set up you may or may not see the .mp3 bit. Usually it’s hidden as you don’t normally need to know that, it is just there for the computer to know which CODEC to use when you play it back. You can rename the files when it is copied onto your PC. So a typical you might rename a sound file to something useful like: RubySaysHello.mp3

Compression

	Some sound file formats are very small and efficient and the technique used to achieve this is called compression. This is something you do after you have edited your sound file and save the final version. Compression is a big subject but it is interesting to understand just a little of what’s going on...
Formats such as mp3 & wma use a cunning technique based on a mathematical model of the human ear. For example it is known that your ear cannot perceive very quiet high frequency sounds if there is a dominant loud drum roll, so the sound compressor doesn’t bother encoding the high bit at all, after all what you can’t hear you won’t miss.

Summary of file types

As mentioned above there are several types but these are the ones you will commonly come across:

Types		Example	Features
wav	wav = wave	RubySaysHello.wav	Best quality but large files, not so suitable for web use. Not Compressed at all.
~
mp3	mp3 = MPEG Layer 3	RubySaysHello.mp3	Good quality and good compression makes this a popular choice. Non proprietary (open for all to use without licensing) Creates files about 1/10th size of ‘wav’ types.
~
wma	wma = Windows Media Audio	RubySaysHello.wma	Features similar mp3 and is proprietary to Microsoft
~
m4p		RubySaysHello.m4p	Improved mp3 with 'Digital Right Attributes' i.e. licensing control. Used by music download sites. Tricky to convert to other formats

What type of digital voice recorder

There are many models available and if searching the web, search for ‘Digital Voice Recorder’.

Before you select a model here are some of the features to look out for.

Must have a: USB connection to your PC External microphone socket Headphone socket Good to have: Integrated speaker Record level indicator Fast/Slow playback Conference mode Easy to use controls Long record time Good battery life Not much use to you: Stereo (but does no harm) Also: Make sure the battery type used is readily available locally for out, most use AAA alkaline batteries.

The sound recorders that other parrot speech group members use can be seen in the groups database.  If you are already a group member try  CLICKING HERE to take you there.

For you guys in the USA, here is a link to Wal-Mart's range of 'Digital Voice Recorders'.  CLICK HERE

 

Can I use an old style tape recorder

Overview only:   Well the short answer is yes but to get the sound on to your computer involves a bit more work.   All modern computers have a 3.5mm microphone socket but these are too sensitive to connect directly to the tape recorder.  However most computers also have a 'Line In' socket  which is less sensitive than a microphone input and that is the one to use to connect your tape recorder to the PC.  You will need a 3.5mm to 3.5mm stereo or mono lead.  Many laptops and some PCs combine both the microphone socket & Line In socket into one and the switch is typically made using the properties of the sound card or via a sound interface program.

But that's the easy bit, just plugging the recorder into your PC doesn't make a digital sound file you need to run a program such as Windows Sound Recorder or a freebie sound recorder program such as HQ-Recorder or Audacity which is also an editor.  The windows sound recorder on Vista is not as good as the XP version and both can be tricky to locate.  Click here for more info. You can purchase an additional box of tricks that you plug your recorder into and that then connects to the PC via a USB lead and it will come with its own software to create digital sound files.  Some are popularly sold as tools to convert your old LPs into computer sound files.  However these are $20+ and you'd be better saving your money to get a digital recorder (see above) which can start as low as $30 unless you have a lot of LPs to convert that is.

Internal or external microphone?

CLICK HERE to go back