9TH GRADE · MECHANICAL WAVES AND SOUND
Sound, echo and resonance
Pitch, volume, timbre, ranges and reflection of sound.
The entire theory of the lesson is collected here; you can read it without an account. In interactive mode, the same theory appears as cards, followed by questions. with checking the answer and task, and progress is saved.
Basic Concepts
Pitch, volume and timbre
Pitch is primarily related to frequency, loudness is related to intensity, and timbre is related to the spectral composition of sound.
The same note of different instruments differs in timbre due to different sets of overtones.
Infrasound and ultrasound
Infrasound has a frequency below the human audible range, and ultrasound has a frequency above it.
Ultrasound is used in diagnostics and echolocation, taking into account the intensity and safety of the effect.
Sound reflection and echo
An echo is a sound that returns after reflection with a noticeable delay.
The distance to the obstacle is equal to half the path of the sound during the time between the signal and the echo.
Physical quantities
Sound frequency
The frequency of vibration of the source and sound wave.
Unit: hertz ·
Distance to obstacle
One-way distance from the source to the reflective obstacle.
Unit: meter ·
Lesson formulas
Echo distance
The distance to the obstacle is equal to half the path of sound during its propagation there and back.
Related formulas
The same formulas in the reference, with symbols and units.
Tasks on the topic
Statements, answer options and the walkthrough.