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Saving a Recipe Tape: Analog or Digital?

Grade 8 practice comparing analog and digital signals with a tape copy test, a noisy-signal model and a claim-evidence-reasoning task.

Grade 8ScienceInteractive · Printable

Aligned toMS-PS4-3

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What’s included

Single worksheet
Auto-graded online
1 NGSS standard
Printable answer key
11 questions
Classroom-ready

Details

Format: Interactive · Printable
Grade: Grade 8
Subject: Science
Question types: Fill in the blank, Multiple choice, Sorting, Short answer

About this worksheet

What students practice

Students use copy-test data to compare how analog and digital recordings hold up when copied.
Students explain why noise changes an analog signal more than a digital signal.

How to use

Read the passage together and point out what changed and what was measured; let students work the signal model in Part 2 with a partner before the written explanation.

Curriculum

NGSS standard covered

MS-PS4-3

Explain why digital signals carry information more reliably than analog signals.

Preview

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Saving a Recipe Tape: Analog or Digital?

Use copy-test data and a signal model to compare analog and digital signals.

Part 1: The tape copy test

Read the passage and the table, then answer the questions.

Nana's Pierogi Tape

1While cleaning out a kitchen drawer, Inés Kowalski found a cassette tape labeled "Pierogi, the real way." Her grandmother had recorded herself explaining the family recipe thirty years ago, step by step, while she cooked. Everyone in the family wanted a copy, and Inés wanted to know which way of copying would keep the recipe clear the longest.

2A cassette stores sound as an analog signal. As the tape is recorded, the strength of its magnetism changes smoothly, following the shape of the sound wave. A tape player turns those smooth changes back into a changing voltage and then into sound. Any extra, unwanted change in the signal, called noise, is played back as hiss or crackle along with the voice.

3Inés planned a test. She played the original tape into a second tape recorder to make copy 1, using a brand-new blank cassette. Then she copied copy 1 onto another new cassette to make copy 2, and kept going until she had five generations of tape copies. Separately, she played the original tape once into a laptop, which stored the sound as a digital file: a long list of numbers written as 0s and 1s. She then copied that file to make five generations of file copies in the same chain, each one copied from the one before.

4To measure clearness, Inés picked a two-minute clip with 150 spoken words. Three relatives listened to every version on the same speaker at the same volume and wrote down each word they could understand. Inés averaged their counts for each version. She used the same clip, the same speaker and the same listeners every time. Only the number of times a version had been copied, and the way it was copied, changed.

5Before the listening began, her cousin Teodor made a prediction. He thought both chains would sound about the same, because every version started from the same voice on the same old tape. Inés was less sure. She knew that tape players and laptops handle sound very differently, and that the old tape already had a little hiss of its own. She wrote down both predictions so the family could check them against the counts in the table below, and she saved the original tape in a dry box in case anyone wanted to repeat the test.