Attenuation

The attenuation is one of the vital aspects of a signal and its transmission. On our attenuation calculator page, you will learn:

• Fascinating facts about attenuation.
• How to calculate component values to design an attenuation circuit.
• How attenuation plays a salient role in daily life.

What is attenuation?

Attenuation is the characteristic of a wave by which it loses its strength with distance. It is the phenomenon opposite to amplification.

Attenuation is measured in decibels (dB) or voltage.

The study of attenuation is important to ensure minimal signal loss in transmission.

Attenuation is an intrinsic property of a medium. The ability of a medium to attenuate sound waves at a given frequency is called its attenuation coefficient (denoted by the Greek letter alpha (α).

The unit of attenuation coefficient is dB / [mHz x cm].

The following image shows the attenuation of electromagnetic energy propagated through the atmosphere at sea level along a horizontal path.

Understanding attenuation

Imagine this scenario:

You are calling out for someone loudly from an audible distance. Now if you move a little further though you call with the same intensity as before, the receiver may not listen to the sound. It is because the sound intensity reduces as it travels more in the medium (here it is air).

This phenomenon is nothing but attenuation (of sound waves in this example).

Every signal that carries energy undergoes attenuation naturally.

In the first instance, it may appear like attenuation is an undesirable characteristic as it reduces the signal strength.

What if there is no attenuation?

Imagine if there is no attenuation:

• The words that you speak keep resounding forever in the air.
• Signals transmitted keep traveling on and on and keep bouncing with each other infinitely.
• If the seismic waves are not attenuated, imagine the loss caused due to earthquakes and tsunamis.
• Confidential information transmitted through signals travels beyond geographical boundaries and poses many threats.

Many such scenarios occur that might hamper the way we live in various ways.

Thus, attenuation is a helpful characteristic which modern technology makes use wisely.

Applications of attenuation

Attenuation finds application in many areas of physics.

Networking

Attenuation in networking can happen because of the type of cable, satellite strength, radio signals, and wireless networks.

Networking experts make sure that signals do not lose notable strength when they are under transmission. They use amplifiers to boost the signal strength all along with the transmission and receiving end.

Oceanography

Water is an excellent absorber of light waves. Ocean water appears in various colors depending on the light absorbed and attenuated.

In the deeper water, most of the components of white light get absorbed except violet and dark blue. It is why deep ocean waters appear in dark blue.

Signal attenuation is also used in radar transmissions and weather studies.

Radio Transmission

Radio signals undergo attenuation while traveling across various mediums including air, concrete, wood, and water. Radio network teams make sure the signal reaches the receiver end by using amplification mechanisms.

Medical Imaging

X-rays and other signals used to study the human body rely on the attenuation principle. High energy photon rays are also used in cancer treatment. However, the energy of photons used in medical imaging gets stored in the human cells. It is why diagnostic and radiation centers are specifically marked as restricted zones in hospitals.

Noise cancellation

Noise cancellation works on the principle of wave attenuation. Hearing protectors and noise cancellation headphones reduce the wave intensity that enters the ears.

Electrical cables

The design of electrical cables is one of the main applications of attenuation. Attenuation in cables is determined by cable type, construction, and material.

Fiber cables offer the least attenuation.

Facts about Attenuation

• Do you know? Attenuation is exponential in nature and is governed by Beer Lambert’s Law
• Attenuation plays a critical role in the impact caused by earthquakes. The seismic waves lose their strength as they travel farther. Hence, the impact of an earthquake is always the highest at the epicenter and decreases with the distance.
• Light is highly resistant to electricity and radio frequency interference. Hence, signals transmitted through fibers undergo the least attenuation. Modern fiber optic cables have an attenuation of as low as 1 dB/km and lesser depending on the distance of separation.
• Aerated Human Lung has the highest attenuation coefficient of greater than 34. It makes it an impermeable barrier for ultrasounds.
• Water and blood hardly attenuate ultrasound waves. They have an attenuation factor of approximately 0.18.
• Copper wires are susceptible to noise. Hence, signals transmitted via copper cables are prone to noise and attenuation.
• For a given transmission distance, high-frequency signals are more easily attenuated than low-frequency signals. This principle explains the preference for low-frequency transducers in signals and circuits.

How is attenuation done in circuits?

Attenuators are passive circuits with four terminals entirely made of resistors. The signal strength is dropped in the form of voltage gain between resistors.

Passive attenuator circuits produce distortion less attenuation.

Active attenuation circuits can also comprise inductors and capacitors. However, they may induce frequency discrimination in the output.

The attenuation of a circuit is measured by the ratio of output/input.

For instance, if the input voltage is 01 volt (10V) and the output voltage is 10 milli-volts (10mV). Then, the amount of attenuation is 10mV/10V is equal to 0.001 or reduced to 1,000th.

The performance of an attenuator is calculated in terms of decibels per decade or octave. It is called Decibel Attenuation.

Decibel Attenuation = 20 log V_out/ V_in (db)

Note: 10 decibels make one Bel.

How to calculate the resistance values needed for an attenuation circuit?

Use our online attenuation calculator to find the values of resistance and capacitance to design an attenuation circuit. Enter the value of input and output impedances and the attenuation in dB.

Our online attenuation calculator gives you the values of various resistors that you may ideally use in shunt and series. Our attenuation calculator online also gives you the Minimum attenuation to achieve impedance match. It also has the provision for quick calculations along with the conversion of attenuation and impedance.

We hope our attenuation calculator online eases your calculations.

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