There are two types of materials based on how they interact with sound waves. Some absorb sound while the others reflect sound. Those that absorb sound make the sound waves lose energy and volume. Materials that reflect sound cause it to continue bouncing around the room.
While both materials are equally as important when it comes to acoustic and sound waves, today, we are going to focus on what materials reflect sound waves best.
Some can be quite good at reflecting sound waves while others are exceptional at it. We want to find out what the very best materials are for this.
In today’s article, we will be looking at different materials and their sound absorption coefficient ratings. These ratings allow us to see the percentage of frequencies that become absorbed by certain materials. These are calculated on a scale of 1 to 10.
For instance, a material that has a coefficient rating of 0.70 means it can absorb 70% of frequencies while reflecting the remaining 30%. Before we find out what the best materials are for reflecting sound, let’s explore the concept of sound reflection itself.
Sound reflection: What is it?
Sound waves never travel in one particular direction with unrestricted movements. They spread all ways from their source. As these sound waves travel, everyday objects become obstacles or barriers.
This often causes the sound waves to bounce back against them before traveling in the opposite direction. This concept is known as “sound reflection” and explains the existence of vibrations and echoes.
Different forms of energy have been found to move in different ways. While sound waves have been compared to light energy, they behave differently. Think of a flashlight that shines into a mirror. Its reflection will be the same as the angle of the incoming ray of light.
The same can’t be said of sound waves, however. When playing music from a speaker, the sound waves will be directed to one area but people can hear the sounds from all areas around the speaker. But sounds do not bounce off all surfaces, even if they travel in all directions.
Some objects absorb sound while others reflect it. So, what materials are best for reflecting sound and making echoes? Let’s find out.
Best sound-reflecting materials
Many materials reflect sound well. Listing all of these materials would have you reading for a very long time. Therefore, we have listed the best and most obvious materials here:
- Ceramic tiles
- Clay brick
- Smooth concrete
Granite is a very dense and heavy material. Like most rocks, it is naturally porous. However, it is usually completely sealed when it arrives in homes making it perfect for sound reflection.
Marble is one of the most reflective surfaces for sound due to its density and strength. It only absorbs around 1% of all frequencies within the 125-2,000 Hz range.
Ceramic tiles have a very low absorption rate. They can absorb up to 2% of all frequencies making them mostly reflective. That’s why you sound so good singing in the shower!
Clay bricks can successfully reflect sounds at most frequencies. Unpainted bricks are capable of absorbing around 3% and 5% of all frequencies. Plaster over concrete will generally absorb between 5% and 10% of all sound frequencies.
Smooth concrete can be as hard and dense as a rock once it is cured. In general, rough concrete can absorb up to 7% of all frequency sounds in the 4,000 Hz range and 4% in the 2,000 Hz range. Smooth concrete is even more reflective as it can bring those numbers down to only 1-2%.
Metal usually boasts a flat and polished surface. This generally makes most metals very reflective against sounds. Steel has a sound absorption of only 0.03 meaning it can only absorb around 3% of all sound waves that come into contact with it. Therefore, it can reflect the other 97% of sound frequencies.
Plastic may be pretty malleable on the whole but it is also rigid and smooth enough to reflect sound waves. As it is pretty dense and non-porous, plastic can reflect up to 95% to 100% of all sounds that come into contact with it. However, for this effect, you’d need to be surrounded by plastic walls.
Glass surfaces are similar to metal surfaces as they also have a coefficient rating of 0.03. But, this can depend on the type of glass. For instance, 4mm of glass can absorb up to 30% of low-frequency waves and 2% of high-frequency sound waves. Thicker glass can reflect between 90% and 98%.
Plywood can reflect between 70% and 91% of sounds with a coefficient rating of 0.30. Solid timber is even more reflective as it can reflect between 86% and 92% of sound frequencies.
Many materials reflect sound wave frequencies but best tend to be stone objects or materials that are dense and very strong.