How Do Wireless Headphones Works? Since the 1960s, wireless headphones have been available. Bluetooth wireless headphones, on the other hand, entered the market in 2004 and revolutionized personal audio listening, quickly gaining popularity among audio consumers and professionals alike. This article is for you if you’ve ever wondered how your wireless headphones or earbuds play back audio from your device.
How do wireless headphones function? Wireless headphones function by receiving wireless signals from their paired audio sources. The source device encodes these signals, which are then transmitted via radio frequency (common) or infrared (less common) carriers. The RF or IR signal is received by the headphones and converted to audio.
This article will go over wireless headphones and how they work. We’ll talk about wireless transmission methods, wireless headphone designs, and the benefits and drawbacks of going wireless.
How Do Wireless Headphones Function?
Wireless headphones, as the name implies, receive audio signals wirelessly rather than through headphone cables (also known as “hardwired” headphones).
Wireless headphones include built-in receivers that accept wireless waves carrying the audio signal intended to drive the headphone drivers. The carrier wave is an apt name for this “wireless signal.”
Transmitters convert the audio signal into a wireless format (the carrier wave) and transmit the wireless signal through the air.
The modulating signal refers to the intended audio signal. This modulating signal is encoded into a carrier wave and wirelessly transmitted to the receiver.
Wireless headphone signals are transmitted using carrier waves that are either radio or infrared in frequency. By clicking the links in this paragraph, you can skip ahead to the sections of this article that explain these carrier waves in greater detail.
Within the aforementioned frequency ranges, the carrier wave is a single-frequency wave. Audio signals are typically composed of frequencies ranging from 20 Hz to 20,000 Hz.
The wireless receiver decodes the modulating signal (audio signal) from the carrier wave. Wireless receivers must be tuned to accept the carrier wave frequency specified.
The digital audio signal is converted into an analog audio signal. The analog audio signal is then amplified to properly drive the headphone drivers.
It is important to note that regardless of the type of wireless headphones used, the fact that they are wireless indicates that the headphone is active. To put it another way, they require power to function properly.
To maintain the headphones’ “wirelessness,” power must be supplied by internal batteries. These batteries could be AA, AAA, or batteries inserted into the headphones. Today’s wireless headphones, on the other hand, are more likely to have built-in rechargeable batteries.
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To summarize, here are the sequential steps involved in wireless headphone audio transmission
- The audio source sends its audio signal to a wireless transmitter.
- The wireless transmitter converts the audio signal (modulating signal) into a carrier wave.
- This single-frequency carrier wave travels through space.
- The wireless receiver, which is tuned to pick up the single-frequency carrier wave, accepts the wireless signal and effectively decodes the audio signal.
- A digital-to-analog converter converts digital audio signals to analog signals (if the headphones are designed for it).
- An internal amplifier boosts the analog audio signal.
- The amplified audio signal is routed to the headphone drivers.
- Headphone drivers (transducers) convert the audio signal (electrical energy) into sound (mechanical wave energy).
Wireless headphones function in the same way as wired headphones, with the exception of how the audio signal is transferred from the source to the headphones and the internal DAC/amplifier.
Modulating Signals and Carrier Waves
Understanding carrier waves and modulating signals is essential for fully comprehending wireless headphones and wireless audio transmission in general. Carrier waves, as the name implies, transport the audio signal from the transmitter to the receiver. Carrier waves are electromagnetic waves that have been modulated with an information-carrying signal in order to be used for wireless transmission.
Electromagnetic waves are produced by the vibration of an electric charge. Electric and magnetic components are present in these electric charge vibrations. These waves transport energy from one location to another. This could be the Sun’s heat and light reaching the Earth, or wireless audio from a transmitter to a headphone receiver.
Unlike sound waves, which are mechanical waves, electromagnetic waves can travel through a vacuum and do not directly interact with medium molecules (though the atoms within a medium will absorb some of the electromagnetic wave energy).
Wireless headphone carrier signals are typically either radio waves (common) or infrared waves (rare).
Radio frequencies (RF) range from 30 hertz to 300 gigahertz (GHz) (300,000,000,000 Hz). The infrared (IR) frequency range is 300 GHz to 430 THz.
Whether the headphones use RF or IR, the carrier wave is a sine wave with a signal frequency. The transmitter is tuned to send this single-frequency carrier wave, and the receiver is tuned to receive it.
Wireless headphones typically operate at or near 2.4 GHz (radio frequency), providing a great wireless range of up to 91 meters (300 ft).
The modulating signal is used to modulate the carrier signal, as the name implies. This modulating signal is then effectively carried from the wireless transmitter to the receiver by the carrier wave.
The modulating signal in the case of wireless headphones is the audio signal intended for the headphone drivers. The modulating signal can modulate the carrier wave in a variety of ways.
Analog Audio Transmission Over Wireless
Frequency modulation is the most commonly used method for wireless analog audio signal transmission to headphones. Yes, the same transmission is used in FM radio, making our RF FM headphones essentially a mini radio station!
The modulating signal modulates the frequency of the carrier wave in frequency modulation (FM). If we sent a simple audio sine wave, the resulting frequency modulated signal would look like this:
As a result, once modulated by an audio signal, the “single-frequency” carrier wave must operate across a range of frequencies. The modulated carrier wave’s bandwidth is accepted by the receiver.
The audio signal is only amplified after the headphones receiver demodulates it, which keeps the variation in the carrier wave frequency low and concise.
Audio signals from headphones are almost always stereo. Fortunately, stereo audio can be transmitted using FM carrier signals. This is accomplished by multiplexing and demultiplexing prior to and following the frequency modulation process.
Multiplexing is the process by which multiple mono or stereo signals are combined into a single signal. The actual FM modulation and demodulation processes in stereo and mono are identical with proper multiplexing and demultiplexing.
Transmission of Digital Audio Wirelessly
Many headphones are now designed to accept digital audio wirelessly, thanks to the rise of digital audio and digital audio devices.
In essence, digital audio is a digital representation of analog audio. Analog audio is made up of continuous alternating current waves. Digital audio captures and digitally represents instantaneous snapshots of the amplitude of an audio signal.
The sample rate and bit-depth of digital audio determine its quality. The sample rate is the number of individual audio amplitudes sampled per second. 44.1 kHz and 48 kHz are common sample rates. In this case, Hz stands for samples per second.
The bit-depth specifies the number of bits used to represent the amplitude of a given sample. The number of binary digits (1s and 0s) chained together to represent a value is referred to as a bit. The most common bit depths are 16-bit (65,536 distinct values) and 24-bit (which has 16,777,215 distinct values).
The greater the resolution and, in theory, the higher the quality of the digital audio signal, the higher the sample rate and bit-depth. It should be noted that higher sample rates and bit depth necessitate more processing power, and that different sample rates may be incompatible with one another.
Bluetooth is the most commonly used method for wirelessly transmitting digital audio to headphones. In our section How Does Bluetooth Transmit Audio From A Device To Headphones, we’ll go over Bluetooth in greater detail.
However, because Bluetooth is so popular, we’ll discuss the actual digital transmission method used to transmit audio from a device to a pair of Bluetooth headphones for the time being.
The most common method of wirelessly transmitting digital audio is pulse-shift keying (PSK) modulation.
PSK modulates the phase of a single-frequency carrier wave to transmit digital data. Modulation is achieved by varying the sine and cosine inputs at specific times.
PSK transmits digital data by modulating the phase of a single-frequency carrier wave. Modulation is accomplished by varying the sine and cosine inputs at a precise time referenced to the binary code of the digital signal.
The Transmitter (Part 1)
The wireless transmitter is in charge of converting the audio signal to a wireless format. We learned in the previous section that this involves modulating a carrier wave with the audio signal.
Transmitters can be standalone devices or plug-in devices for audio sources. These wireless headphone transmitters are commonly used in the home and with professional in-ear monitoring systems.
Transmitters can also be built directly into audio devices. This is true for the vast majority of wireless devices, and it is always true for Bluetooth devices.
Transmitters are typically designed to send either analog or digital audio signals wirelessly and operate within a limited frequency range that corresponds to a compatible receiver.
The carrier signal frequency in some transmitters can be altered or “tuned” to a specific frequency by the user.
Part 2: The Recipient
Wireless headphone receivers are integrated into the headphones. There are also standalone wireless receiver units that can be used with wired headphones, though these systems are not entirely “wireless.”
A receiver is designed to effectively pick up the carrier wave transmitted by the transmitter. The audio signal is then decoded from the carrier signal.
As previously stated, wireless transmission requires that the receiver and transmitter be tuned to the same frequency.
Specific types of modulation are decoded by receivers. Analog receivers generally decode FM signals in order to be compatible with transmitters (in the radio frequency range). Digital receivers, on the other hand, are typically used to decode PSK signals (also in the radio frequency range).
PSK receivers in Bluetooth headphones, for example, accept RF frequencies ranging from 2.400 to 2.4835 GHz.
What Is the Process of Radio Frequency Transmission?
To recap, radio waves are electromagnetic waves with frequencies ranging from 30 Hz to 300 GHz.
These electromagnetic waves carry energy with them and cause electric and magnetic field oscillations in their path. They naturally emit in all directions and travel at the speed of light in a vacuum. Electromagnetic waves travel more slowly in mediums like air due to interference from the medium’s molecules, but they are still extremely fast.
When we talk about infrared wireless headphones, keep this definition of electromagnetic waves in mind.
Returning to RF transmission
Although the RF spectrum extends from 30 Hz to 300 GHz, most RF headphones operate between 900 MHz and 3.2 GHz, depending on the model. The Bluetooth wireless standard operates at frequencies ranging from 2.400 to 2.4835 GHz.
RF wireless headphones frequently wirelessly receive analog audio signals. As previously stated, these signals are transmitted wirelessly using frequency modulation:
- The modulating signal is the audio signal (typically covering the frequency range of 20 Hz to 20 kHz).
- The carrier wave is a sine wave with frequencies ranging from 900 MHz to 3.2 GHz.
- The frequency of the carrier wave is modulated by the amplitude of the audio signal.
- The modulated carrier wave is received by the headphones, and the audio signal is extracted from the carrier wave.
The Sennheiser RS 175 Headphones are an excellent example of RF wireless headphones
The transmitter must have a multiplexer to effectively combine the left and right channel signals into a single modulating signal in order to send stereo audio signals (which can be thought of as two separate mono signals). Similarly, the receiver must have a demultiplexer to split the signal back into stereo so that the left and right drivers can be driven.
Because radio frequencies are so effective, they are frequently used to transmit audio and other signals.
Because of their relatively long wavelengths (in comparison to other electromagnetic waves, not sound waves), they can travel long distances and penetrate solids (walls, floors, etc.). A typical 2.4 GHz RF wireless transmitter can send signals up to 91 meters (300 feet).
If all of the RF receivers are tuned to the same frequency, RF transmission waves can be picked up by an almost infinite number of them. The theoretical limit is only a result of the physical space required by a receiver in relation to the volume of the RF carrier wave’s distance range.
However, the popularity of RF wireless has a significant disadvantage. This disadvantage is that RF headphone signals are susceptible to interference from all other devices that transmit audio over RF signals at or near the transmission frequency.
What Is the Process of Infrared Transmission?
Infrared (IR) waves are electromagnetic waves with frequencies ranging from 300 GHz to 430 THz. Because IR waves have higher frequencies than RF waves, they have shorter wavelengths. Let’s talk about how IR waves behave differently than RF waves.
The fact that IR is line-of-sight distinguishes it from RF. There will be no signal transmission if any physical objects eclipse the IR transmitter from the IR receiver.
This is primarily due to the short wavelengths and weak infrared waves.
Another disadvantage of short infrared waves is that their transmission range is only about 10 m (32 ft) as opposed to the 91 m (300 ft) or more that RF has.
This short-range line-of-sight is a significant disadvantage for many applications, but it can be a significant benefit when privacy is desired. In most cases, IR headphones are used in small rooms and wirelessly connect to televisions and other sound sources in movie theaters, boardrooms, and courtrooms.
How Does Bluetooth Transmit Audio From A Device To Headphones?
Now comes the fun part. Bluetooth has become the de facto standard for the vast majority of wireless headphones, so it’s critical that we discuss it here.
To begin with, the Bluetooth standard is constantly being improved, and there are numerous versions. The Bluetooth Special Interest Group and the engineers who work on Bluetooth technology ensure version compatibility. When we pair two devices with different Bluetooth versions, we only get the benefits of the oldest version.
There are numerous standards within the overarching Bluetooth standard, which can be perplexing. Please bear with me if you’re a Bluetooth expert as I focus on the standards commonly used for Bluetooth headphones. Everyone else should be aware that other standards exist, and that any given pair of Bluetooth headphones may not fit the exact description I’ll be providing here.
Now, let’s look at how Bluetooth headphones [generally] work!
Bluetooth functions by pairing devices. To transfer information (audio), the headphones must be paired with a Bluetooth-enabled device.
Using Wireless Headphones with a TV, Radio, or Other Device
It is possible to connect wireless headphones to devices by pairing two Bluetooth devices.
If the devices have other wireless connection means (RF or IR), we can connect them simply by turning on the transmitter and receiver and matching the frequencies.
If the devices do not have Bluetooth or another compatible built-in wireless system, we will need to connect a standalone transmitter and/or standalone receiver to the device and/or standalone receiver to the headphones.
To begin with, we’d like to have wireless headphones with built-in wireless receivers. However, wired headphones can connect to receivers that make at least part of the signal path wireless.
Fortunately, most RF and IR wireless headphones come with their own dedicated transmitter. This makes connecting the headphones to the transmitter simple and solves our problem by ensuring the transmitter can connect to our device (TV, radio, etc.).
Typically, the transmitters will connect to the device via an analog connection such as a left/right RCA audio out or 3.5mm TRS stereo out.
The Benefits and Drawbacks of Wireless Headphones
To follow up on the previous section on wired vs. wireless headphones, let’s quickly go over the advantages and disadvantages of wireless headphones.
Wireless headphones have the following advantages:
- Many of today’s popular audio devices are compatible with the common Bluetooth standard (which is now used in most new wireless headphones).
- Being untethered from the audio device.
- Bluetooth (Class 2) typically has a range of up to 10 m (32 ft).
- RF (at about 2.4 GHz) has a range of 91 m (300 ft) or more.
- IR has a range of up to 10 m (32 ft).
Wireless headphones have the following drawbacks:
- Batteries are required for operation and must be replaced or recharged on a regular basis.
- The Bluetooth standard depletes the battery of the paired device as well.
- Because of the built-in receiver and amplifier, the price is higher (and potential DAC).
- When compared to wired headphones, it can be difficult to connect quickly.
FAQs About How Do Wireless Headphones Works
How do wireless headphones communicate with one another?
How Do Wireless Headphones Work? Image result for
Pull down the shade from the top of your Android device and long-press the Bluetooth icon. It will take you directly to the Bluetooth menu, where you can turn it on and search for devices. Tap the name of the headphones you’re attempting to connect.
Is WiFi required for wireless headphones?
Bluetooth operates on short-range radio waves rather than an internet connection. This means that Bluetooth will work anywhere two compatible devices are present — no data plan or cellular connection is required
What’s the distinction between Bluetooth and wireless headphones?
The main distinction is how the headphones connect to a media player. Wireless headphones can use radio waves, infrared, internal memory, or Kleenex to transmit audio signals, whereas Bluetooth headphones use short-range radio waves.
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