Sound
Every day your ears are flooded with music, talking, sirens, and laughter. But what actually is a sound? It is entirely invisible, yet it can travel across huge distances, rattle the windows of your house, and even let you hear things around corners! Let us explore the invisible world of vibrations and waves.
What Exactly Are You Hearing?
No it cannot! Sound waves need a physical material to travel through. Because outer space is a completely empty vacuum with no air molecules, there is absolute silence in deep space.
It travels much faster through solid metal! The molecules in metal are packed very tightly together, allowing the invisible sound vibrations to bounce between them extremely fast.
Put Your Instincts to the Test
Think about what you already know about music and noises. Pick an answer for each question, then see if your instincts were right.
An object must vibrate back and forth! Absolutely every single sound in the universe begins with physical movement and vibration.
Very fast vibrations! The faster an object vibrates back and forth, the higher the pitch of the sound it makes.
The eardrum! This delicate piece of skin acts exactly like the top of a musical drum, vibrating when sound waves crash into it and sending those signals to the inner ear.
Understanding the Science
Let us break down the invisible waves, vocal cords, and echoes with Bill Nye the Science Guy.
Key Concepts
Vibration
Tap to learn moreA vibration is a rapid back and forth movement. Absolutely every single sound in the universe starts with something vibrating!
Sound Wave
Tap to learn moreA sound wave is the invisible ripple of energy that travels outward from a vibrating object. It pushes through the air molecules around it like a falling domino knocking over the next one.
Medium
Tap to learn moreA medium is the physical material that a sound wave travels through. Sound can travel through gases like air, liquids like water, and solid objects like wood or metal.
Vacuum
Tap to learn moreA vacuum is a place with absolutely no matter or air molecules at all, such as deep outer space. Sound cannot travel through a vacuum because there is nothing for the vibrations to push against.
Pitch
Tap to learn morePitch is how high or low a sound seems to your ear. It is completely determined by how fast or slow the object is vibrating.
Frequency
Tap to learn moreFrequency is the scientific measurement of how many sound waves pass a point in one single second. Fast vibrations create high frequency waves, while slow vibrations create low frequency waves.
Eardrum & Cilia
Tap to learn moreThe eardrum is a delicate piece of skin deep inside your ear. It acts exactly like the top of a drum, catching sound waves and vibrating to send signals to tiny microscopic hairs called cilia, which translate those vibrations for your brain.
Echo
Tap to learn moreAn echo is a sound wave that bounces completely off a hard, flat surface and travels right back to your ears so you hear it a second time.
Try It: The Interactive Audio Visualiser
Take control of the invisible forces of sound! Press the Play button below to generate a real audio tone. Use the custom orange sliders to adjust the frequency for pitch and the amplitude for volume. Listen to the physical sound change while you visually compare how the air molecules squeeze tightly together and spread far apart!
Apply Your Knowledge
Let us see if you can match these wave properties to the sounds they create.
Match the Concepts
Click an object to select it, then click the matching description to place it.
Real World Challenge
Imagine you have been hired to design a professional recording studio for a famous musician. Knowing how sound waves bounce off hard surfaces, what specific materials would you put on the walls and ceilings to stop annoying echoes and keep outside noises from getting in?
What Has Changed Since This Episode Aired
This episode first aired in the 1990s. While sound waves still bounce and vibrate the exact same way, modern engineers have invented brilliant new technologies to manipulate those invisible waves!
Updated: Engineers have perfected active noise cancelling technology! Modern headphones use tiny microphones to listen to outside noise, and then they instantly create an exact opposite sound wave to completely cancel out the unwanted noise before it even reaches your eardrum.
Updated: Yes! Doctors are now using extremely powerful focused ultrasound waves to safely burn away dangerous tumours deep inside the body without ever having to make a single physical cut in the patient.
Updated: Modern submarines and robotic boats use highly advanced sonar systems. They bounce millions of tiny sound waves off the bottom of the sea to create incredibly detailed three dimensional maps of dark ocean trenches and sunken shipwrecks.
Test Your Understanding
Answer these questions and get instant feedback. How many can you get right?
Results
Your score:
Reflection
Think about all the different sounds you can make with your mouth, lips, and vocal cords. If you had to describe what a sound wave is to someone who had never heard one before, what analogy or comparison would you use?
Episode Discussion
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