Sound: String Length and Pitch | Virtual Science Teachers

Sound: String Length and Pitch

Pluck the strings of a virtual harp to investigate what makes a sound high or low.

Investigate this question

How does the length of a harp string affect the pitch (frequency) of the sound it makes?

Student View

Teacher Graph and Notes

Use this as a quick reference while students graph and explain their results.

What students should notice

The line curves downward. Shorter strings have higher frequencies and higher pitches. Longer strings have lower frequencies and lower pitches. Possible claim: As string length increases, frequency and pitch decrease.

Why use a line graph?

Both variables are numerical. Students should plot one point for each string, order the points from shortest to longest, and connect adjacent points. They should not draw one straight best-fit line. A bar graph is better when the horizontal axis contains separate categories.

Why the curve is scientifically appropriate

For a string fixed at both ends, f = v ÷ (2L). The simulation holds tension and string thickness constant, so wave speed stays constant and frequency varies inversely with string length. In these data, frequency × length is approximately constant.

Model limitation

Real harp strings may also differ in tension and thickness. This model keeps those factors constant so students can isolate the effect of string length.

Exact graph values

Note	A4	G4	F♯4	E4	D4	C4	B3	A3	G3
Length (cm)	35.6	40.0	42.4	47.6	53.4	59.9	63.5	71.3	80.0
Frequency (Hz)	440.00	392.00	369.99	329.63	293.66	261.63	246.94	220.00	196.00

How to use this

Click a string, or use a note button, to pluck it.
Watch it vibrate and listen to the pitch.
Read that string's length and frequency.
Compare a long string to a short one.
Use your data as evidence for the question.

Options

Show wave on string Pluck strength (also changes loudness)

Last string plucked

Length

Frequency

Pluck a string

Your data

Pluck a string to start collecting data.

Background

Key vocabulary

Vibration: A repeated back and forth motion. Plucking a string causes it to vibrate.
Pitch: How high or low a sound seems to your ear.
Frequency (Hz): How many vibrations happen each second, measured in hertz.
Amplitude: The size of a vibration. Bigger amplitude usually sounds louder.
Wave: A disturbance that transfers energy from one place to another.
Transverse wave: A wave where the material moves perpendicular to the direction the wave travels. The vibrating string is a transverse wave.
Longitudinal wave: A wave where the material compresses and spreads parallel to the direction the wave travels. Sound moving through air is a longitudinal wave.

Science concepts

When a harp string is plucked, it begins to vibrate, and that vibration is what produces sound.

Plucking a string transfers energy to the string and starts its vibration.
The vibration pattern on a string is a type of standing wave, because the wave reflects back and overlaps with itself between the fixed ends.
The frequency of the vibration is what determines the pitch you hear.
Strings vibrate differently depending on length, thickness, and tension.
In this simulation, thickness and tension stay the same, so you can focus on how length alone affects pitch.

Write your CER

You are answering this question

How does the length of a harp string affect the pitch (frequency) of the sound it makes?

Claim

Write one clear sentence that answers the question.

Sentence starter

When the string length ____________, the pitch and frequency ____________.

Evidence

Use data from the simulation to support your claim. Include at least two specific examples with string lengths and frequencies.

Sentence starter

In the simulation, when I plucked a string with length ______, its frequency was ______ Hz.

When I plucked a shorter string with length ______, its frequency was ______ Hz.

Reasoning

Explain why the pattern happens, using science ideas about vibrations. Connect string length to vibration rate to frequency to pitch.

Sentence starter

This evidence supports my claim because ____________.