RUNNING HEAD: CORDLESS HEADPHONES
CORDLESS HEADPHONES: PHYSICALLY POSSIBLE
Anthony Davis
Dutchess County Community College
Physics Department
General Physics 122
Authors Note:
This assignment is being submitted on March 27, 2015, for Professor Renee
Lathrop’s PHY 122, General Physics 2 course.
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CORDLESS HEADPHONES: PHYSIALLY POSSIBLE
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TABLE OF CONTENTS
…...................................................................................................................................Page
Purpose…………………………........................................................................................3
Introduction………..………..............................................................................................3
The Electromagnetic Spectrum……………..…………………......................................3
Sound Deliverance Through Radio Waves…..................................................................4
Sound Deliverance Through Infrared Waves….............................................................5
A Brief Mention of Bluetooth Technology………………...............................................6
Limitations to the Study…………………………………………………………………6
Suggestions for Further Research……............................................................................7
Conclusion……..................................................................................................................7
References……..................................................................................................................8
CORDLESS HEADPHONES: PHYSIALLY POSSIBLE
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PURPOSE
To further appreciate the everyday use of ordinary objects one must understand
the physics involved, therefore this paper provides a look at the physics involved with
cordless headphones. Upon completion of this paper, readers will have a detailed answer
to the question: How do cordless headphones physically work?
INTRODUCTION
Without a second thought, headphones, in the absence of a cord, are placed upon
the head and sound begins to stream into the ears upon the press of a play button. Is it
really this simple? The answer to the question is no because physics plays such a huge
role in the working of cordless headphone technology. In general, a base unit is plugged
into an audio device, which translates audio sound into an alternate form, this alternate
form is then sent to the receiver end, which then translates it back into audio sound. As
stated earlier, this process is not so simple. Other elements involved in the process are the
electromagnetic spectrum in a general sense, radio waves in some cases, infrared waves
in some cases, and, in some cases, Bluetooth technology. The following information will
describe in detail how each play a role in the physics of cordless headphones.
THE ELECTROMAGNETIC SPECTRUM
The electromagnetic spectrum is an organized grouping of wavelengths or
frequencies. Starting from radio waves, it continues to infrared waves, visible light,
ultraviolet, x-rays, and ends with gamma rays. (Cutnell & Johnson, 2012) For the purpose
of this paper, the focus will stay on radio waves and infrared waves because transmitters
transmit sound to receiver in cordless headphone technology via either radio waves or
infrared waves. The other portions of the electromagnetic spectrum focus on a wide
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variety of other aspects ranging from color transmission to imaging, etc. The following
pictures serves to provide a visual of the electromagnetic spectrum:
(LBL, 2009)
SOUND DELIVERANCE THROUGH RADIO WAVES
One way in which sound is delivered to cordless headphones is through the
transmittance of radio waves. Radio waves are noted as the longest waves on the
electromagnetic spectrum with wavelengths ranging from one millimeter to one hundred
kilometers. Contrary to their long wavelengths, they exhibit the shortest frequencies, with
frequencies ranging from 10ˆ4 Hz to approximately 10ˆ11.5 Hz. (Cutnell & Johnson,
2012) These waves are important to the physics behind cordless headphones because they
are one way in which sound is transferred from base unit to receiving unit.
First a radio transmitter is plugged into the audio devices headphone jack with a
built-in radio frequency receiver and this connection helps to establish an electrical
impulse. (Lilley, 2015) This impulse provides the initiation of conversion of audio signal
coming from the audio device to radio waves via the excitement of electrons within an
antenna attached to the base unit (either external or internal). These radio waves then get
CORDLESS HEADPHONES: PHYSIALLY POSSIBLE
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sent through the air to the headphone portion of the unit (the receiving end) or the
antenna attached to the receiving end. Again through electron excitement via passing
radio signals within the antenna, radio waves are then converted back to audio sound.
This audio is cleared of noise, static and out-of-frequency interference. Speakers within
the headphone unit receive these newly established electrical signals and use
electromagnets to create physical vibration on the speaker membranes, which are then
transferred through the air to the listener who receives it as audio sound. (Evans, 2015)
This type of transmission of sound is ideal for outdoor cordless headphones use because
of the long length of the radio waves, as well as, their ability to travel through walls and
other obstructing objects such as clothing.
SOUND DELIVERANCE THROUGH INFRARED WAVES
Alternative to radio wave use, cordless headphones can also function through the
use of infrared waves. Infrared waves are waves on the electromagnetic spectrum with
wavelengths ranging from 10ˆ-3 meters to approximately 10ˆ-6.2 meters. These waves
exhibit frequencies longer than their radio wave counterparts with frequencies ranging
from approximately 10ˆ11.5 Hz to approximately 10ˆ14.6 Hz. (Cutnell & Johnson, 2012)
These waves are important to the physics behind cordless headphones because they are
another way in which sound is transferred from base unit to receiving unit.
Like the radio wave transmission, a base unit is plugged into a sound or audio
device with a built-in transmitter. However, unlike radio wave transmission, LED (lightemitting diodes) is used to transmit a beamed signal (of pulsating invisible light) from the
base unit to the receiving unit (the actual cordless headphones/or an antenna attached to
them). These pulsations of light provide the audio signal to the cordless headphones that
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then travel through the air as sound, from the speakers of the headphones to the ears of
the listener. This type of technology usually permits approximately thirty feet of range
before sound quality becomes distorted. (Kayne, 2015)
These waves cannot travel through walls and other obstructing objects because
the blocked beam prevents the transmission of infrared waves, so it serves better for inhome cordless headphone use. In addition to this, they also serve better as indoor
headphones because sunlight exposure weakens infrared waves and could distort intended
sounds. Although these things hold to be true with infrared cordless headphone
technology, a stereo signal is sent to the receiving end of the headphones when using
infrared technology and therefore delivers good sound quality to the listener, which
provides for a great benefit to the listener. (Kayne, 2015)
A BREIF MENTION OF BLUETOOTH TECHNLOGY
As a brief mention, there are also devices that function off of Bluetooth
technology, which also use radio waves to transmit sound from base unit to receiving
unit. They utilize ultra high frequency short waves in the industrial, scientific and
medical band from 2.4 GHz to 2.485 GHz. (Poole) This method of transmission only
permits short distance transmission. The greatest benefit of Bluetooth is that it makes for
a simple connection from device to headphones through easy device menu selection.
LIMITATIONS TO THE STUDY
This study focused on the physics behind cordless headphone and did not touch
upon the mechanics involved in manufacturing cordless headphones. Also, this study did
not look at the differences between the terms cordless and wireless and instead used the
terms synonymously by only using the term cordless. In addition to this, the study did not
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explore the different brands of cordless headphones, in terms of finding any differences
in physical properties used to provide functionality. Lastly, the research did not explain
how sound is further transmitted though the auditory canal within the human body.
SUGGESTIONS FOR FURTHER STUDY
A suggested area for further study would be to provide a look at the mechanics
involved in manufacturing cordless headphones, which will incorporate other aspects of
physics, such as forces. Another suggestion for further study would be to take a deeper
analysis of radio waves and infrared waves to further explore their role in cordless
headphone technology. In addition to this, an area of continued study would be a look at
the health risk involved with over exposure to the waves mentioned in this paper in an
effort to promote further research in utilizing physics to provide safer usage methods.
One last area of continued study would be to take a look at the physics involved in the
transmission of sound waves in the auditory canal once they exit the speaker apparatus’
attached to cordless headphones.
CONCLUSION
Whether it is radio waves, infrared technology or Bluetooth technology, cordless
headphones all work because of the various physical properties mentioned in the paper.
Because this technology exits, advancements in the fields of health, gaming, cell phones,
and music have occurred. By understanding the physics involved in cordless headphones,
users are better equipt to safely use these technologies as well, in terms of taking the
precautions to avoid over exposure to the various waves mentioned in this paper. Lastly,
thanks to the many strives made in the field of physics cordless headphones are
physically possible.
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REFERENCES
1. Cutnell & Johnson. (2012). Physics- 9th Edition. Hoboken, NJ: John Wiley &
Sons Inc. (pp. 739 – 767)
2. Evans, Kieth. (2015). “How wireless headphones work”. http://www.ehow.
com/how-does_4897473_how-wireless-headphones-work.html. Accessed on
February 26, 2015.
3. Kayne, R. (2015). “What are infrared headphones”. http://www.wisegeek.com/
what-are-infrared-headphones.htm#didyouknowout Accessed on March 1, 2015.
4. LBL. (2009).“Electromagnetic Spectrum”. http://www2.lbl.gov/MicroWorlds/
ALSTool/ EMSpec/EMSpec2.html. Accessed on March 26, 2015.
5. Poole, I. Bluetooth radio interface, modulation, & channels”.http://www.radioelectronics.com/info/wireless/bluetooth/radio-interface-modulation.php. Accessed
on March 27, 2015.