If you live in an apartment, the common question is how much you can hear from someone living downstairs or upstairs.
A typical apartment building has a shared wall, which means that the sound from the other doors can reach your ears once they make a noise. It is easy to hear the loud stereo or people shouting living next door.
Some apartments have a drop ceiling that also works as an acoustic underlayment.
But how about the sound from upstairs, or downstairs, if you are on the second floor? Does sound traveling work the same way wherever you are in a room? How does noise travel?
What do we know about sound waves and vibrations?
While sound does not travel in one direction or a straight line, we have to dig deeper into the concept of sound.
Pro tip: Do you know that the reason why megaphones are cone-shaped is for sound to travel in a particular and directional area? Because the megaphone physically directs where the sound will go.
How Sound Travels
Before we can understand how far sound can travel or its direction, we need to know the simple facts about sound waves.
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What are Sound Waves?
Sound waves are best represented by moving particles in matter. For example, on a solid matter, like a pole, intact with atoms or particles.
When you poke the pole, thus creating sound for the first time, you are pressing the atoms or applying force (creating vibration) for them to move. When particles are pushed, they bounce. Thus, the bouncing particles represent sound waves.
However, the speed of movement of the atoms depends on the type of material.
Materials like solids, with particles intact, will make the sound speed faster than the particles on wood and air.
Sound transmitted from the impact of an object is called structure-borne noise. On the opposite, airborne noise or airborne sound is a sound directed to the air, such as speech and music.
In simple perspective:
- Vibrations produce sound.
- Sound waves are particles that are called bouncing atoms of vibrating particles.
- The speed of sound is dependent on the type of surface it pokes.
How far Does Sound Travel?
The answer to this question is complicated because there are many variables at play. To understand this better, let’s say that sound travels depending on the phase of matter it will pass through.
- Sound waves travel at a speed of approximately 332 m/sec in air.
- But it travels faster through liquid and fastest in solid.
- If objects hit one another, you are generating an impact sound or impact noise.
Do all Sounds Travel the Same Distance?
Perhaps, the better question would be, “do all sounds travel at the same speed?” The answer is no because it depends on the type of medium they travel.
As explained above, it is more difficult for sound waves to pass through gas or air, and liquids than solid materials. Ironic, right? Because solids, as we know them, are non-permeable materials.
However, since sound vibrations are flowing, they are more effective in passing through and bouncing back if the medium is harder or has more intact atoms.
To illustrate this, imagine throwing a ball into the air or the water and then comparing which medium the ball came back to faster. The ball, representing the sound wave, travels most quickly in solids.
Meaning sounds pass slower in liquids and slowest in air. That’s why when you are in an open space and you shout, the listener will hardly hear you more than when you are in a closed room. The walls in that space absorb the sound coming from you and reflect it to the listener.
How does Sound Travel Through Floors?
If your apartment has levels, it is divided by drywall and wood floors. Also, you will be wondering how sound travels through floors and if they do.
We will take a similar concept about sound traveling on solids. However, this is quite a complex matter because there are many situations at play.
Let us learn from them, and then we can infer the manner of sound travel.
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Sound travels in any direction, meaning it is omnidirectional. But different factors affect their speed.
- Though sounds can be primarily heard through solids, this doesn’t mean you can listen to the noise from a different floor, whether upstairs or downstairs.
- Since floors are partitioned by a solid matter in the form of wood or hardwood floor, they will block the sound from within a room traveling to the downstairs apartment.
- The sound is reduced when the source is closed, and you are not in that space. This explains that the sound made in that room is absorbed by the closed door, leaving less or no space for sound waves to travel. That’s why you hear a little when people are having a conversation in a closed room.
- But if a sound is produced directly hitting the floor or dropping something on it, the sound source travels now to the floor and then through the listener.
- Sound travels through floors, but its speed and level vary depending on the medium used.
PRO TIP: Does sound travel upwards? No, because sound waves are omnidirectional. They travel in all directions.
Does Sound Travel Through Walls?
With the same concept of sound traveling through the floors, yes, sound also travels through walls.
So when your child is playing loud music in the other room, you can hear it unless that room is soundproof or insulated to enclose the sound for better quality. Soundproofing is a way to reduce the impact of unwanted noise.
Sound can travel through depending on how much the room is insulated. Sound insulation is an effective way to enhance or lessen sound.
Sound Reflection and Absorption
Reflection and absorption are two elements or acoustical tools that absorb and reduce the strength of sound.
Photo Credit: Acousticsciences
We use sound absorbers to reduce or eliminate sound.
- Sound absorbers are like when your wall has a hole in it. And when you throw the sound, it will dissipate in a vacuum.
- A sound absorber will completely destroy the noise so it won’t reach its listener in a crisp sound.
- Objects with curved and uneven shapes can serve as sound reducers. They are called curved surface diffusers. Why?
- The curves on the surface reduce the vibration. It lessens the strength of sound rather than eliminating it.
So in a room where you desire to eliminate noise, you use a combination of diffusers and absorbers. And this is explained in the sound-deadening article we previously discussed.
Now you know how the room next door is set up if you hear a loud noise.
Why does Sound Travel Faster in Warm Water?
In basic science, water molecules in warm or hot water move faster than in cold water because they have more energy to transmit vibration within particles quickly.
So, if the water becomes ice, it is now in solid form. And from that, we can say that the molecules hardly move and cause vibration.
Relevant Questions on Sound That Require Answers
Do higher-pitched sounds travel faster?
No. Higher-pitched sounds equate to high-frequency sound waves. Low-frequency or low-pitched sounds like bass will travel faster and downward due to gravity.
Practically speaking, it is like comparing a heavy stone, and a tin can simultaneously drop. You know which drops faster.
If you have a family member, who gets annoyed with the loud bass sound from your subwoofer, install bass traps in your room.
Why are you more likely to hear noise from an upstairs apartment than from downstairs?
Because the people upstairs can direct the foot traffic, causing the sound and noise downwards. Unless the floor has carpet padding, so, your lower-floor apartment dweller will hear your footsteps and furniture moving.
Apartment living is different from single-attached home living when it comes to hearing sounds and background noise.
Why does sound only travel from upstairs neighbor to downstairs and not vice versa?
Sound will not travel up or down. It travels in all directions unless something redirects it. As mentioned, the speed and direction of sound will depend on the medium it is applied to.
How much noise travels upwards to a second-floor apartment from the first floor?
This would be explained by understanding the concept in number 2.
It is actually the reverse of the idea that those on the second floor can create more sound as the floor joist (the ceiling on the first floor) receives the sound directly from foot traffic, while no sound stimulant will directly hit the joists of those on the first floor.
This will also answer that a top apartment won’t be less noisy than the bottom. Indeed you will have noisy upstairs neighbors. The same with the downstairs neighbor.
If you can hear your downstairs neighbor talking, can you also hear me talking?
This depends on where you are.
If you are in the same room, of course, you will be heard. But if you are on the upper floor, it still depends on how loud you talk, how much furniture you have, and how rich the volume you have in your speakers.
Floor underlayment also adds sound insulation, especially if it serves as acoustic insulation or acoustic underlayment.
PRO TIP: Frequency is measured in Hertz (Hz) units. It measures sound speed in radios, giving amplitude modulation (AM) and frequency modulation (FM).
Now you know the answer to sound travel upstairs or downstairs.
Generally, the discussion about sound and sound speed is a broad topic. But there are ways we can improve the transfer of sound in a particular area if that is our aim.
Yet, to understand the technicality of sound direction, adapting to the nature of your room and the objects in that room that will receive the sound will help you achieve a quieter room and get rid of noises in the neighborhood.
Next time, you’ll know why there is a noisy neighbor on the lower or upper floor.
Robert is an electronic engineer with more than five years of experience with a solid affinity for helping people reduce noise. He writes about these silent home appliances and easy soundproofing measures to help everyone avoid the negative effect of extended exposure to high noise levels.