ITPEC FE Subject A October 2024 Question 17
Topic: MultimediaAlso asked in October 2018 and Spring 2020
Audio signals are recorded using 8-bit samples at a sampling rate of 11,000 times per second. When a flash memory of 512 × 106 bytes is used, what is the maximum recording time of such data in minutes?
Explanation
775 minutes — each 8-bit sample is 1 byte, so the recording consumes 11,000 bytes every second.
- •Data rate: 1 × 11,000 = 11,000 bytes per second
- •Seconds: 512 × 106 ÷ 11,000 ≈ 46,545 s
- •Minutes: 46,545 ÷ 60 ≈ 775.8, so 775 whole minutes fit
Answer (c)
Why not others:
- •(b) 96 — treats each 8-bit sample as 8 bytes, 775.8 ÷ 8 ≈ 96.97
- •(a) 77 and (d) 969 — factor-of-ten slips on the values behind (c) and (b): 775.8 ÷ 10 and 96.97 × 10
Key rule: Data volume = bytes per sample × samples per second × seconds; convert bits to bytes and seconds to minutes once each, and check the powers of ten.
Multimedia · AI-written, may contain errors
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