← IGCSE Computer Science Paper 1

Acoustic sensor

A sensor that detects sound and measures its level. Used in noise monitoring, burglar alarms and glass-break detection to show how loud a sound is or whether a sound is present.

Part of: IGCSE Computer Science 0478 — 3.2 Input and Output Devices — Module 34, IGCSE Computer Science 0478 — 6.1 Automated Systems — Module 19

Understanding Acoustic sensor in IGCSE Computer Science Paper 1

What it does: The acoustic sensor captures the sound level as data, which is stored in a variable for the noise monitor to use. Noise monitoring should respond to a loud sound with a suitable output such as a warning message or alarm, for example SoundAlarm() or DisplayWarning().

Common mistakes: An IF statement needs THEN after its condition. The line should be IF level > 80 THEN. A burglar alarm should sound when the sound level is above the threshold, not below it. The condition should be sound > 60.

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This module's key terms are also in a printable crossword (Modules 273–282) and word search (Modules 262–282).

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Learning

Duo

What does an acoustic sensor detect?

SoundLight

Matches

humidity ← ReadAcousticSensor()

↓

An acoustic sensor detects sound, not humidity, so the data captured is the wrong type

Applying

Meanings

Term

acoustic sensor

Meaning

A sensor that detects sound and measures its level. Used in noise monitoring, burglar alarms and glass-break detection to show how loud a sound is or whether a sound is present.

Practice

SoundLevel ← ReadAcousticSensor()

Testing

Gaps

IF soundLevel 80 THEN

Check Answer

Spots

1level ← ReadAcoustic()

2IF level > 80

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Quick Questions

1. What does an acoustic sensor detect?

A. Light

B. Sound ✓

An acoustic sensor detects sound and can measure how loud it is.

2. Which data can an acoustic sensor capture?

A. The level of a sound ✓

B. The pH of a liquid

Acoustic sensors capture sound level, or whether a sound is present. A pH sensor measures acidity.

3. A burglar alarm uses an acoustic sensor. What is it listening for?

A. A sound such as breaking glass or a forced door ✓

B. A change in air temperature

In a burglar alarm the acoustic sensor detects unexpected sound, which the microprocessor can use to trigger the alarm.

4. A school wants to check how loud its canteen gets at lunchtime. Which sensor is the best choice?

A. Acoustic sensor ✓

B. Pressure sensor

Noise monitoring needs the sound level to be measured, so an acoustic sensor is used.

5. Which statement is true?

A. An acoustic sensor can only measure the temperature of a room

B. An acoustic sensor can detect that a sound is present ✓

Acoustic sensors capture sound data. They can show whether a sound is present and how loud it is.

Match the Pairs

IF soundLevel > 85 THEN → The acoustic sensor reading is compared with a limit to check whether a noise is too loud

IF soundDetected = TRUE THEN → The acoustic sensor reports that a sound is present, for example in a burglar alarm

A noise monitoring system uses an acoustic sensor to measure how loud the sound is → noiseLevel ← ReadAcousticSensor()

A glass-break detector sets off an alarm when its acoustic sensor picks up a loud, sharp sound → IF soundLevel > 90 THEN SoundAlarm()

humidity ← ReadAcousticSensor() → An acoustic sensor detects sound, not humidity, so the data captured is the wrong type

IF soundLevel > 85 THEN LightOn() → The output does not match the purpose of a noise monitor, which should warn about loud sound not switch on a light

Key Term

acoustic sensor

A sensor that detects sound and measures its level. Used in noise monitoring, burglar alarms and glass-break detection to show how loud a sound is or whether a sound is present.

Fill in the Blanks

1. IF soundLevel > 80 THEN OUTPUT "Too loud" ENDIF

Hint: Type the comparison operator that means greater than, so the warning runs when the noise is above the limit.

2. IF soundLevel > 80 THEN OUTPUT "Noise warning" ENDIF

Hint: Type the pseudocode keyword used to display a message to the user.

3. alarm ← FALSE IF soundDetected = TRUE THEN alarm ← TRUE

Hint: Type the Boolean value that means the sensor has detected a sound in a burglar alarm.

4. WHILE monitoring = TRUE DO soundLevel ← READ_SENSOR(acoustic) ENDWHILE

Hint: Type the loop keyword that keeps checking the sensor again and again while monitoring is on.

5. limit ← 85 soundLevel ← READ_SENSOR(acoustic) IF soundLevel > limit THEN

Hint: Type the variable name that stores the loudest sound level allowed; it is used again in the IF test below.

Spot the Error

Question 1

A level ← ReadAcoustic()

B IF level > 80

C OUTPUT "Too loud"

D ENDIF

Line B — An IF statement needs THEN after its condition. The line should be IF level > 80 THEN.

Question 2

A REPEAT

B sound ← ReadAcoustic()

C IF sound < 60 THEN

D SoundAlarm()

E ENDIF

F UNTIL FALSE

Line C — A burglar alarm should sound when the sound level is above the threshold, not below it. The condition should be sound > 60.

Question 3

A glass ← ReadAcoustic()

B threshold ← 90

C IF glass >= threshold THEN

D OUTPUT Glass break

E ENDIF

Line D — Text to be output must be in quotation marks. It should be OUTPUT "Glass break".

Question 4

A WHILE monitoring = TRUE

B dB ← ReadTemperature()

C IF dB > 85 THEN

D OUTPUT "Noise warning"

E ENDIF

F ENDWHILE

Line B — A noise monitor must read the acoustic sensor, which measures sound level. A temperature sensor cannot measure noise. It should be ReadAcoustic().

Question 5

A reading ← ReadAcoustic

B IF reading > 70 THEN

C OUTPUT "Loud sound"

D ENDIF

Line A — The function call is missing its brackets. It should be ReadAcoustic() so the sensor reading is returned.

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