Sound file sizes and the quality of playback questions and answers
Q1. What factors might affect the size of a sound file?
A1. Sample rate, sample resolution and the way that the file is compressed.
Q2. A sample rate is given as 65KHz. Write this out in words.
A2. Sixty Five thousands Hertz.
Q3. What is meant by codec?
A3. This is a maths formula that takes a large 'raw' file recording and cleverly squashes it. A sound codec such as MP3 or OGG will greatly reduce a raw file size for hardly any loss of quality.
Q4. What is meant by ‘streaming music’ and describe how it works.
A4. Streamed music is where you listen to the music as it is downloaded from the Internet as opposed to downloading and saving the whole song first and then playing it. As the first few seconds of a streamed song is downloaded, it is put into a special storage area called a 'buffer' and then playing starts. While that part of the song is played, more of the song is being downloaded and buffered.
Q5. What is meant by ‘file compression’?
A5. Applying a maths formula known as a codec to make the file smaller.
Q6. What is the difference between a ‘lossy’ codec and a ‘lossless’ codec, giving examples of each?
A6. One type of codec is called 'lossy compression'. The maths formula for these seek to remove the parts of a sound file which are deemed relatively unimportant, for example, sound samples that are out of the range of the human ear. Some popular lossy codecs include MP3 and OGG (Ogg Vorbis). Another type of codec is called 'lossless compression'. These codecs keep all of the information about a sound file. The file format WAV is an example of a lossless codec.
Q7. What is an 'analogue' signal?
A7. This is a signal that has an infinite number of possible values.
Q8. What is a 'digital' signal?
A8. This is a signal that can only be either one or zero.
Q9. What is the difference between sample rate and sample interval.
A9. Sample rate is the number of readings you take in a unit of time whereas the sample interval is the time between readings.
Q10. What does 'ripping a CD of music' mean?
A10. Ripping a CD of music means converting it into a more readily playable format such as MP3 or OGG.