WHAT’S THIS? …..

WHAT CHANGES? Uptown Funk 1 Uptown Funk 2. Uptown Funk 3

LESSON OUTCOME I understand and can explain how sound is stored by a computer system.

WHAT DO I NEED TO KNOW AT GCSE? (a)Explain how sound can be sampled and stored in a digital form (b)Explain how sampling intervals and other considerations affect the size of a sound file and the quality of its playback I understand how sound is stored by a computer system.

THEORY NOTES Sound just like images are stored in binary format that is then read and interpreted by a computer with the use of metadata. Sound is often a continuously varying data (analogue) but a computer needs this in binary format so it needs to be transferred from analogue to digital form. To do this we sample the sound wave at set intervals and record the values, this set of values is saved and replayed by the computer. I understand how sound is stored by a computer system.

BAR CHARTS - TWO SAMPLING RATES

SO WHAT'S THE DIFFERENCE? Uptown Funk at “Normal” 96000hrtz sampling and bit rates. Uptown Funk at “Half” 48000hrtz sampling and bit rates. Uptown Funk at “Quarter” 24000hrtz sampling and bit rates. I understand how sound is stored by a computer system.

TASK Add a description to your graphs about what we have just discussed. You can use the notes below to help you; The sample rate affects the quality of the sound, a high or more frequent sample rate improves quality as it is closer to the original but involves a larger file size. A lower sample rate will have reduced quality as it is less close to the original however the trade off is a lower file size.

BIT RATE The bit rate is the amount of data that can be used to store each sample. So as before a higher bit rate will lead to better quality playback but will require a large file size, a lower bit rate will reduce the file size but result in lower quality playback. I understand how sound is stored by a computer system.

IMPORTANT – KEYWORDS Don’t confuse sample rate and bit rate! They are different. The sample rate is how frequently the data is sampled. The bit rate is the amount of data stored at each sample point. I understand how sound is stored by a computer system.

QUESTIONS How does the sample rate affect the quality of the playback for an MP3 sound track? What factors affect the file size for a sampled MP3 track? Why are there so few tracks on a typical audio CD? Which sound file formats (MP3, WAV etc.) sample most frequently and less frequently? I understand how sound is stored by a computer system.