How do Speakers Produce Sound: The Science Behind Sound Production

Irfan KhanOctober 31, 2022November 7, 2023

Have you ever wondered how speakers produce sound? It’s actually a pretty complex process, and there is a lot of science behind it.

In this blog post, we will discuss the basics of how speakers work and what goes into making them produce sound. We will also take a look at some of the different types of speaker technologies on the market today.

Plus, you will also get to know a little bit about the history of speakers and their physical composition. In the end, you will also get some useful tips on getting the best music from your speakers!

So, if you’re curious about how your favorite speakers create that amazing sound, keep reading!

Table of Contents

History of Speakers
Components of a Speaker
How do Speakers Produce Sound?
How to Make your Speakers Sound Better?
Binaural Sound: A New Sound Frontier
Frequently Asked Questions
Summary

It would be unfair to talk about how speakers make sound without mentioning the basic development and structural system of speakers. So, let’s start with some basics.

1. History of Speakers

In 1861, the first public speakers were made by Johann Phillips Reis, but they created muffled sounds.

A significant development for speakers happened in 1877 when Werner Von Siemens unknowingly developed the future speakers and didn’t even realize it. He was the first to use electromagnetic coil-driven speakers but failed to commercialize them.

After this breakthrough, it took another 48 years for Rice and Kellogg to patent their moving coil technology. Their speaker made use of a permanent magnet and induction to move the coil and diaphragm that produced sound waves.

Speaking of the first, the Radiola loudspeaker #104 was the very first speaker to be included in a radio.

2. Components of a Speaker

Now that you know the historical development of speakers, let us discuss the different components of speakers.

1. Diaphragm

The diaphragm is also called the speaker cone. It is the actual component that moves back and forth, creating sound waves. It is also connected to the basket and the voice coil and is the visible part of the speaker.

2. Dust Cap

The dust cap is put in the middle of the diaphragm to keep dust and other things from getting into the speaker.

3. Surround

A surround is a piece of elastic material that connects the diaphragm to the basket. It joins the outer and inner frames.

4. Basket

The basket acts as the robust framework around which the speaker is constructed. It serves as the housing for the speaker components.

5. Suspension

Suspension, also known as a “spider,” is a flexible and corrugated support that limits the movement of the speaker driver in all directions except vertically upwards and downwards as it receives audio signals.

6. Magnet

A permanent magnet made of ferromagnetic material is used to surround the pole piece. The diaphragm moves when the magnetic fields of the voice coil and the permanent magnet interact.

7. Lower Plate

The bottom plate is made of soft iron. It acts as the basis for the other components of the speaker. The pole piece and the permanent magnets are placed on it

8. Pole Piece

The voice coil is wound over the pole piece with cylindrical cardboard or another insulator material in between them.

9. Voice Coil

The voice coil is a wound wire that receives the audio signals and moves the diaphragm back and forth. It is also called a speaker driver. It is the voice coil that moves the speaker cone.

3. How do Speakers Produce Sound?

Now that you know the essential topics for understanding speakers’ work, it’s time to get into the science behind sound-making.

1. Sound and Audio

You may think that sound waves or sound energy are the same things as an audio signal. Well, they’re actually different! To learn how speakers function, it is necessary that you differentiate between the two.

So what is a sound wave? Sound energy is composed of mechanical waves. For something to go from one place to another, it needs to pass through a medium (solid, liquid, or gas).

The sound waveform includes characteristics like frequency, amplitude, and wavelength. And the energy of the wave causes distortion of the medium it’s traveling through. That’s all you need to know about sound waves. On to the audio signals!

Sound waves are translated into an electrical signal known as an audio signal. The differences in sound pressure levels (SPL) are what audio signals show. The audio signal is then used by the transducer or driver to move the diaphragm, which in turn produces sound waves.

2. Working Principle of Speakers

A speaker converts electrical energy to mechanical energy. But you may wonder how? Well, a magnetic field is created in the voice coil as electricity flows through its wires. Then the voice coil’s magnetic field interacts with the permanent magnet’s magnetic field.

3. Mechanism of Sound Production

We have already discussed that the magnetic field is produced around the driver or voice coil when current flows through it. Because of the alternating current, the magnetic fields in the coil will change as the audio signals pass through them.

Voice coils generate both positive and negative magnetic coil cycles. Yet a permanent magnet’s magnetic field never changes. So, there will be times when the poles of the two magnets line up, causing them to pull toward each other.

Plus, when two magnets’ magnetic fields are perpendicular to each other, they will also push against each other. The voice coil vibrates because of the magnetic fields’ attractive and repulsive forces.

Based on the waveform of the audio signal, the voice coil will oscillate between 20 Hz and 20,000 Hz. Is that all it takes to create sound, you may ask? The answer is no! The voice coil’s motion is insufficient to generate audible sounds on its own.

However, the voice coil is linked to the thin diaphragm that can move back and forth. As the diaphragm moves with the voice coil, it causes small pockets of air to move, which creates mechanical waves.

So you can say that sounds from the speaker are transmitted via sound waves, which travel to your ears, and that’s when you enjoy your favorite song! Quite fascinating, right? It certainly is!

4. How are Sounds of Different Volume and Frequency Generated?

In the previous section, you learned how sound is produced. But what about the songs that have beats and the rises and falls in their tunes? Well, let’s figure out how you hear such diverse and beautiful music from your speaker!

One thing that you know at this stage is that if the cone of a speaker vibrates vigorously, the output sound will be loud, whereas muffled sounds come from weak vibrations. Also, bigger electrical pulses are sent to make louder sounds, and the same is true for quieter sounds.

a) Drum Skin Analogy

You can better understand this behavior by using a drum analogy. When you hit the drum hard, the sound it makes is much louder and clearer than when you hit it softly. Therefore, more energy must be provided to generate a loud noise.

This follows the principle of energy conservation. Guitars and drums have a screw that you can adjust to change how much the string or skin is loose or tight. If you keep them tight, you will get faster vibrations, which results in higher-pitched sounds.

And if you keep the string or the skin loose, the vibrations are much slower and have a lower frequency. So now you know that the speakers use the same kind of mechanism to make sounds at different volumes.

So, the volume is all about how strongly or softly the diaphragm vibrates. But wait, this is not enough to fully understand the different frequencies coming from your speaker. Speakers cannot be adjusted like guitars or drums, so there must be something else at play inside them!

b) Woofers and Tweeters

So how does your favorite speaker create those beautiful notes of low and high frequencies? It’s not hard to do at all. Speakers are of two types based on cones. Those with larger cones, known as woofers, move slowly and generate deep bass.

The speaker produces low-frequency sounds as the cone moves slowly. Similarly, high-frequency sounds are produced by smaller speakers with smaller cones. A tweeter is a type of speaker driver that produces sounds at high frequencies by rapidly moving the diaphragm.

You might be wondering how woofers and tweeters work together perfectly in a speaker when they sound so different. Since the sounds coming from your speaker are perfectly synced, you don’t even notice that there are actually two speakers at work.

That’s due to the clever use of crossover circuits! The electrical signal in a standard speaker is split between low and high-frequency drivers via a special circuit. The high-frequency signals are directed toward the tweeters, and the low-frequency ones are directed toward the woofers.

5. What is Frequency Response, and Why is it important?

So, what is the frequency response, and why is it important? Well, it is a measure of a speaker’s ability to reproduce audio waveforms. If the airwaves match the sound waves in frequency and amplitude, then the speaker is good.

Simply put, if your speaker’s sound wave has all of the frequencies in the audio waveform, you’re getting the best music experience. All the frequencies must be reproduced; if some are absent or extra frequencies are introduced, the speaker is not up to par. The quality of this replication is due to a number of things, including frequency response.

The frequency response of a speaker tells you how loud different sounds will be at different frequencies. As part of standard frequency response testing, frequencies from the low, middle, and high-frequency ranges are sent.

During the trial, any changes in the speaker’s voice are recorded and checked. The ideal speaker would produce a consistent sound across a wide range of frequencies. This is called “flat response,” and it means that you will hear the music as it was created for you!

6. Why are Speakers Mounted in a Box?

You might wonder why your speaker is put in a box if it only uses the mechanism we’ve talked about. The box takes up more space and costs you more money. So, let’s dive into the science of speaker containers.

When the diaphragm vibrates, there will be pressure waves in both directions. Going forward creates positive pressure, and going backward creates negative pressure. Because of this, the longer wavelengths of sound will almost cancel each other out at a great distance.

This effect specifically cancels out the low-frequency bass, rendering it inaudible. You can listen to your speaker in its assembled and unassembled form to see the difference in sound. Despite coming from the same speaker, you will notice a big shift in the audio quality.

7. Why do some Speakers have Holes in them?

You may have noticed something else about speakers that seems strange at first glance. Most speakers have holes near the diaphragm on either the top or the bottom of the enclosure.

Do you ever wonder if their sole purpose is purely decorative? Or they are required for the rich sound as well? Keep reading to find out!

8. The Bottle Music and Speaker: How Resonance Works

Have you ever tried blowing air into a bottleneck that was already open? Depending on the size of the neck, it gives a specific tone. The hole in the speaker boxes works like a resonance system, making frequencies with different levels of pitch.

In that open bottle, the sound is determined by the length of the bottle’s neck and the amount of liquid within. Your speaker dimensions work in a similar way, producing sounds at different frequencies by altering the size of the port and enclosure.

So how does this come into play inside the speaker? Well, the bass response is determined by the size of the port, which acts as a bottleneck, and the enclosure, which acts as the volume of the bottle. These holes make the bass response of your speakers much better.

How to Make your Speakers Sound Better?

There are multiple ways to improve the sound of your speakers. You will learn a few important methods in this section.

1. Sympathetic Resonance

You already know the reason why the enclosure is needed for speakers. Let’s move on to another big reason why the containers make your speakers sound the way they do.

The cone’s resonant vibrations are only one part of the way sound reaches your ears. To a greater or lesser extent, the air around the waves will begin to vibrate in sync with them as the sound waves are produced.

To understand this concept, consider a guitar. As the strings vibrate, the air inside them starts to vibrate in response. This creates a pressure wave that amplifies the sound wave. This process is called sympathetic resonance. It enables the sound waves to get louder and travel farther.

For speakers, the sound that reaches your ears is amplified by the casing. Find an old radio or speaker and try it out on your own. Listen to it in the enclosure, then dismantle it and try it out. That whole, resonant sound will no longer be heard.

2. Earphones vs Speakers: How Sound is Perceived?

If you want to make your speakers sound better, you should also know how people perceive sound. An earphone transmits sound straight to your ear canal. But whenever we discuss speakers, they are always off in the distance.

There is complete coverage of the room with the speaker’s sound. The sound waves interact with the room’s furniture and physical objects as they reflect off of walls, ceilings, and floors.

The sound that speakers produce and we hear is significantly altered by these interactions. You may test this for yourself by comparing the sound quality of music played in a full versus empty room using a set of speakers. There is a significant contrast between the two sounds.

3. Arrangement of Speakers

Sound quality is also greatly impacted by how your speakers are set up. It also depends heavily on your tastes and inclinations. So, you can try different methods until you find the arrangement that gives you the best experience!

To identify the best setup, you can use a set of factors. To give an example, moving the speakers to different places can change the sound quality. Spread your speakers out evenly over the room if you like.

For instance, if one of your speakers is positioned centrally on one side, the other should be positioned front and center on the other side. So, the reflected sounds won’t change the sound coming from the original speaker. Similarly, you can also experiment with speaker stands.

In many cases, they significantly enhance the audio quality of the speakers. Try out different things until you find the best setting for your room. Once you find that perfect setup for your room, things will change. You will appreciate your music and movies even more than before.

4. Types of Sounds and Their Quality

In reality, a wide variety of sounds can be heard. Commonly used sound formats nowadays include mono, stereo, quad, and binaural. When first introduced, speakers were mono, with a single fixed source and varying sound quality depending on the listener’s location.

Through the introduction of 2-dimensional sounds, Stereo enhanced the quality of mono. But the best experience of sounds is through 3-D sounds. It is possible to convert stereo to 3D by using several speakers, but doing so is quite expensive.

In a Quad sound system, the front and rear channels are reproduced by two speakers each. You can experience true 3-D audio, with the sound that can actually surround you. Cinematic surround sound is a common application of Quad Sound.

8. Binaural Sound: A New Sound Frontier

You may have heard of binaural sounds somewhere. Thanks to binaural sound, you can hear recordings in 3-D with just two speakers. But how does it work? Our outer ear’s (pinnae) natural ridges and troughs are the basis for its working. To create a more lifelike sound in binaural recordings, a dummy head is used that mimics the dimensions of the human ear.

To get a feel for this revolutionary technology, check out some binaural recordings on YouTube or other internet resources. When comparing stereo and binaural sounds, you will notice a big difference.

Frequently Asked Questions

Q: How fast does my mobile speaker vibrate?

A: Your mobile speakers can vibrate between 20 Hz and 20 kHz. Mid-range woofers produce sounds from 300–500 Hz up to 5,000–6,000 Hz.

Q: What are the common problems that my speaker can develop?

A: Your speaker could have problems like poor frequency response, no bass, or distorted sound. The sound quality can also be affected by a broken transducer or by running the speakers at a high volume most of the time.

Q: How can my speaker get damaged?

A: Several factors can be responsible for damaging your speakers. An electrical surge can damage the speakers irreversibly. Water can damage the circuitry of the speakers and cause a blowout.

Q: How long will my new speaker last?

A: Speakers are pretty durable. If you have a good-quality speaker, it can last quite a while. Based on environmental conditions and other factors, good speakers can last 40–50 years before any signs of damage.

Summary

Why is it worth knowing how your speakers work and how the different parts come together? Well, it has multiple benefits for you. For instance, if you’re looking for a dope sound system, then now you can pick and choose the best components to build your perfect sound system.

And now that you’ve read about the science behind speakers, you will be able to differentiate between good and bad speaker systems. Plus, you will also be aware of what parts contribute to the sound you want. And the best part is, you can now steer clear of snake oil salesmen and bad experiences.

Finally, you can attempt to build your own speakers as well. So, apply your imagination with this knowledge and you’ll have a fun experience building your own speakers!

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