omputer-science/aqa/questions","basePath":"/gcse/computer-science/aqa/representing-sound/questions","formulaUrl":null,"initialIndex":23,"initialQuestionWindow":[{"id":"97a415c5-9d1d-44a2-ae84-a50ca2cba263","revisionId":"30b6e799-14d2-4b87-942e-ed23305ee924","questionNumber":null,"questionType":"LA","specification":"A marine biologist is recording underwater whale vocalizations using a specialized hydrophone. The single-channel (mono) audio is captured with a sampling rate of 12,000 Hz and a sample resolution of 24 bits.","difficulty":3,"difficultyBand":"medium","totalMarks":4,"sourceTitle":null,"calculatorUse":null,"parts":[{"id":"2ce32292-78e1-41e8-bfcd-5934225c3ee7","label":null,"content":"Calculate the minimum file size of a 15-second audio recording. Give your answer in **bytes**.\n\nYou should show your working.","markscheme":"- Shows substitution of correct values into the file size formula: $12,000 \\times 24 \\times 15$ (or equivalent) M1\n- Calculates the correct intermediate value, either the total bits ($4,320,000$ bits) or converts the resolution to bytes ($24 \\div 8 = 3$ bytes) A1\n- Shows division by 8 to convert bits to bytes (e.g. $4,320,000 \\div 8$) OR shows direct multiplication of bytes (e.g. $12,000 \\times 3 \\times 15$) M1\n- State the correct final answer of $540,000$ (or $540,000$ bytes) A1","marks":4,"order":0,"markingRubric":null,"explanation":null,"options":[]}],"options":[],"explanation":null,"firstAttemptFullMarks":null},{"id":"995a0e6d-66d4-49b7-bf57-11af4a072d9b","revisionId":"363163a8-990a-4c87-919c-92f62d776494","questionNumber":null,"questionType":"LA","specification":"A bioacoustics researcher records the low-frequency vocalisation of a blue whale using a single-channel hydrophone.\n\nThe recording is configured with a sampling rate of 48,000 Hz and a sample resolution of 24 bits. The captured sound clip lasts for exactly 250 seconds.","difficulty":4,"difficultyBand":"medium","totalMarks":3,"sourceTitle":null,"calculatorUse":null,"parts":[{"id":"065e7d33-ee70-4937-ba93-ca810cf144a5","label":null,"content":"Calculate the minimum file size of the recording in megabytes (MB).\n\nAssume 1 kilobyte (kB) = 1,000 bytes and 1 megabyte (MB) = 1,000,000 bytes.\n\nYou must show your working.","markscheme":"- Calculates the total size in bits by multiplying the parameters: $48,000 \\times 24 \\times 250 = 288,000,000$ bits M1\n- Converts the size from bits to bytes by dividing by 8 (or by converting 24 bits to 3 bytes early: $48,000 \\times 3 \\times 250$): $36,000,000$ bytes M1\n- Converts the bytes to megabytes by dividing by $1,000,000$ to get $36$ MB A1","marks":3,"order":0,"markingRubric":null,"explanation":null,"options":[]}],"options":[],"explanation":null,"firstAttemptFullMarks":null},{"id":"b9ceff31-a64b-45d6-b882-78abecb60259","revisionId":"0dfaed83-f62a-43b9-a96c-32e2df717401","questionNumber":null,"questionType":"MC","specification":"A high-fidelity digital master of a violin solo is recorded with a sampling rate of $96\\text{ kHz}$ and a sample resolution of $24\\text{ bits}$. To prepare the track for a web broadcast, the audio is downsampled to a sampling rate of $48\\text{ kHz}$ and a sample resolution of $16\\text{ bits}$.\n\nWhich option correctly describes the quantitative change in the uncompressed file size and the qualitative effect on the digital representation of the sound wave?","difficulty":7,"difficultyBand":"medium","totalMarks":1,"sourceTitle":null,"calculatorUse":null,"parts":[],"options":[{"id":"472f9c12-d87d-458d-805e-0d5570be7d4c","content":"The file size is reduced to $\\frac{1}{3}$ of its original size. The maximum frequency that can be accurately represented is halved, and the quantisation error increases because there are fewer discrete amplitude levels.","correct":true,"markscheme":"Correct. The file size ratio is $\\frac{48 \\times 16}{96 \\times 24} = \\frac{1}{3}$. Halving the sampling rate halves the maximum representable frequency (Nyquist limit), and

Representing sound

Question 10

Representing sound Questions

Representing sound

Question 10

Representing sound Questions