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Select suitable headphone-Impedance matching

Updated on May 8, 2012

Ever wondered, headphones working well in device properly, giving only non clear sounds when used in other device. For example, suppose the headset you are using in your iPhone is used in a Dell laptop, how will be the sound clarity?. There are some fact that have to be taken care, while purchasing a headset to make sure that you are purchasing a suitable headphone

Impedance matching in hearing devices

For every device there is an impedance. Technically it is the resistance offered to any electrical signal. (Remember that sound signals are in the form of electrical signals up to the time it reaches the speaker diaphragm). Also to get optimum sound clarity, the impedance of the your device and headphone should match. (It is in accordance with maximum power transfer theorem. According to this theorem, to get maximum power transferred to the load, both source and load impedance should match).

Impedance matching mainly comes into play for systems with considerable distance between source and destination. (ie.If the distance between them is comparable with the wavelength of the signal). In this case connecting cable impedance also should match with source and destination impedance. If impedance is not matched, signal will reflect back and forth causing echos canceling some parts of the signal. But this problem comes only in long lines like telephonic lines. This is the problem causing the faint sound at the receiver and on long distance calls.

While purchasing Headphones

While purchasing headphone you have to look for following factors

1. Type of headphone that you are looking for

There is a wide variety of types of headphones available in the market- circumaural (fitting around ear), supraaural (fitting on top of ear), earbuds (placed on the outer ear, not into the ear canal), Inear (These are placed into the ear canal). First of all you have to select which type of headphone you want. Circumaural and supraaural are suitable if you are looking for a headphone for watching movie at home from your laptop or desktop. For both of these versions you will get Bluetooth enabled headphones, which will help you go wireless. But there will be recharging battery inside, recharging it regularly is a pestering thing. For earbud and inear type headphones, Bluetooth variants are not available, but you can get this feature by using Bluetooth connector. These types of headphones are suitable for outdoor uses, for hearing music from mobile, iPod etc

While selecting the type of headphone, you have to check, what kind of connector you have, Currently the most used connector is of 3.5mm jack. If you are not purchasing a headphone with suitable connector, it will of no use as you cannot connect it to the audio device.

Different types of headphones
Different types of headphones

Impedance of your audio device and the headphone that you are going to purchase

According to the famous electronics theory of maximum power transfer, you should have same impedance in your device and for the headphone to get optimum output. But in case of headphones, this impedance matching is not such a serious problem. If you are using a low impedance headphone in a comparatively high impedance device, you can get more sound at lower voltages, This is the technology used in small voltage devices like laptop headphones, mobile headphones etc. But if you connect may of such low impedance audio headphones to the same audio device, source loading will occur.

Sensitivity or efficiency of the headphone is another thing that you have to look while purchasing headphone. It is expressed in dB/mV.

Noise Cancellation or Noise Reduction

This is another useful thing that you have to consider while purchasing headphones. Noise isolation or noise cancellation means to reduce the external sound getting into the ear. Using inear headphones it is easily achieved. As these headphones are used by putting in ear canal, the chance for external noise to come in is very less. Also while using covering type headphone also the chance of sound coming inside is very less. But using inear headphones for a long time will impair your hearing capabilities as these are very near to eardrum. Closed type headphones are the best ones for watching movie purpose. But it is not as much portable as inear or earbud type headphone.

* While using headphones, the presence of bacteria inside ear canal increases soon, So always remember to remove headphones intermittently.

* High levels of volume will damage your hearing ability. It is always better to listen to songs when background volume is less. If you are listening to music in noisy places, surely you will increase the volume to very high levels to hear music more clearly (you wont even notice that it is crossing the normal limits).


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