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Do You Really Know Earphone Specifications

The difference between earphones and headphones

Though one amongst the foremost common things within the audio chain, earphones or headphones might not forever work properly. Common issues square measure distorted audio, low level with the degree at most, or high level with the degree at minimum. This bulletin can justify earphone/headphone specifications, which of them square measure vital, and the way to decide on earphones for Associate in Nursing system.

Let’s differentiate between headphones and earphones. A earpiece consists of 1 or 2 transducers (usually miniature speakers) that square measure connected to a metal or plastic band. This band provides correct placement of the transducers over the ear; the scarf rests on prime or behind the top. There square measure 2 common types: open-back and closed-back. The open-back kind has acoustic ports on the skin that increase bass response, however has the draw back of permitting background signal to bleed through into the ear. The closed kind fully covers the ear, so reducing background signal. A secondary advantage is that sound originating from the headphones won’t radiate outward. Closed-back square measure most popular for applications like studio recording wherever noise should be decreased .

Earphones also are transducers however with no band. they will be placed on the pinna (earflap) or within the acoustic meatus. The former, referred to as “earbuds”, square measure sometimes the alfresco kind, since tiny transducers cannot generate low frequencies while not acoustic ports. The latter, referred to as “in ear” earphones, use a foam or different soft material to carry the electro-acoustic transducer within the acoustic meatus, so uninflected it from close noise. Forming Associate in Nursing acoustic seal makes the acoustic meatus a part of the electro-acoustic transducer “system” and modifies its frequency response. the benefits square measure that less volume is needed, and audio quality is usually higher.

Most earpiece and electro-acoustic transducer specifications show actual ohmic resistance and sensitivity. Some others go a step additional and show maximum/clipping level and frequency response. These specifications outline however every unit can work with Associate in Nursing system. On the system facet, pertinent specifications square measure output ohmic resistance, power output, and/or clipping level.

Impedance

Impedance is opposition to the flow of current. the upper electrical phenomenon, the less current can flow. electrical phenomenon is measured in Ohms, indicated by the Greek sign Omega (Ω). Earphones and headphones vary from eight Ohms to 600 Ohms or higher. The audio supply (the earphone output) additionally has AN electrical phenomenon rating. to get most power transfer (all usable power from the supply reaches the earphones) impedances ought to match. However, that’s seldom the case. once impedances don’t match, there’s either a loss of voltage or of current, in different words, a loss of power. This power loss is calculated with the subsequent formula:

earphone impedance  formula
earphone impedance formula

Where

– RS: supply electrical phenomenon (the impedance of the audio system’s earphone output)

– RL: Load electrical phenomenon (the impedance of the earphones or headphones)

Let’s assume we would like to use earphones with AN electrical phenomenon of a hundred and ten Ohms. If connected to a supply that matches this electrical phenomenon, the higher than formula shows a loss of -6.0 dB. despite the fact that there’s most power transfer, there’s a loss. this can be known as load loss and there’s no thanks to avoid it. as an example, employing a higher supply electrical phenomenon, say 600 Ohms, the facility loss becomes -8.8 dB. this can be nearly three sound unit not up to before; -3 dB represents 0.5 the facility. employing a lower supply electrical phenomenon, say sixteen Ohms, the facility loss is –9.5 dB. Note that the load loss will increase if the supply electrical phenomenon is higher or is not up to the precise phone impedance. Figure #1 shows the facility loss for various earphones driven by different supply impedances.

In most cases, load loss isn’t essential. A earphone electronic equipment usually will deliver much more power than required, therefore overcoming the impact of unmatched impedances.

Power loss at different supply impedances for various earphones.
Power loss at different supply impedances for various earphones.

Sensitivity

Sensitivity is however effectively associate degree earpiece converts an electrical signal into an physics signal. Sensitivity indicates however loud the earphones are going to be for a given level from the supply. ImageThis activity is given in decibels of force per unit area Level per power unit, or sound unit SPL/mW. In some cases it’d be shown as dB/mW and is predicated on a one mW signal. One mW is one thousandths of a Watt, or 0.001 Watts. The sensitivity of earphones is sometimes within the vary of eighty to a hundred twenty five sound unit SPL/mW. Here is associate degree example. associate degree earphone’s sensitivity is 122 sound unit SPL/mW. this implies one mW of power can generate 122 sound unit SPL. This SPL level is over the brink of pain and might cause permanent hearing injury during a short quantity of your time. Figure #2 shows totally different levels in sound unit SPL and therefore the exposure time before hearing injury might occur. A typical earphone output might offer this level. Note that sound unit SPL don’t add during a linear manner; two mW into the earpiece won’t generate 244 dB SPL. Doubling or halving the input power will increase or decreases the SPL by three sound unit. A .5 mW input into the earpiece can generate 119 sound unit SPL. A sensitivity rating doesn’t mean abundant till it’s matched with the output capabilities of associate degree sound system. If a system has low output level, employing a low sensitivity earpiece can lead to low SPL. Increasing the electronic equipment level during this configuration can cause distorted audio thanks to amplifier clipping. On the opposite hand, a high sensitivity earpiece plus a high power headphone electronic equipment can force an occasional volume setting, and than may end up in additional noise. A classic case of this drawback is connecting a try of economical earhones to associate degree aeroplane electronic equipment. Setting the degree at the primary position, right higher than zero, offers enough level however is uproarious. Increasing the degree makes it too loud to use. A simple, passive earphone electrical device solves this drawback by reducing the amount being delivered to the headphones, permitting you to boost the degree of the earphone electronic equipment to a setting that produces less noise. the subsequent table shows the SPL output level for the various earphones at different supply levels.

Sound levels and maximum explosure time
Sound levels and maximum explosure time

Input power (mW)


Earphone #1
113.5 dB SPL/mW


Earphone #2
105 dB SPL/mW


Earphone #3
122 dB SPL/mW

0.1

103.5

95.0

112.0

0.2

106.5

98.0

115.0

0.5

110.5

102.0

119.0

0.8

112.5

104.0

121.0

1.0

113.5

105.0

122.0

1.2

114.3

105.8

122.8

1.5

115.3

106.8

123.8

Frequency Response

When the frequency response is given as a graph, it indicates 2 completely different measurements. One, it shows the vary of frequencies, lowest to highest, reproduced by the earpiece. Two, it shows the relative output level of the earpiece at every frequency. Frequency response is measured in Hertz (Hz) and covers the sonic vary between twenty cycles/second and 20,000 Hz. mensuration frequency response in earphones isn’t a straightforward task. It needs the utilization of a “dummy head”. The dummy head resembles an individual’s head and contains a mensuration electro-acoustic transducer within every meatus. correct mensuration of electro-acoustic transducer frequency response is easy because the headphones are placed over the dummy ears. mensuration earphones could be a completely different matter. once correct earpiece placement is achieved, the meatus becomes a part of the earpiece and affects the frequency response. Since everybody contains a completely different meatus (depth, diameter, curvature, etc.) the frequency response can vary. In fact, it’s doubtless that frequency response can vary between each ears of identical person. Therefore, a frequency response graph for earphones created employing a dummy head isn’t a meaning mensuration.

Clipping Level or most Level

Earphone specifications seldom show clipping level or most input level. However, the audio supply instrumentation would possibly show this specification for the electro-acoustic transducer output. during this case it’ll indicate the amount at that the electro-acoustic transducer electronic equipment begins to clip and therefore the audio signal becomes perceptibly distorted. counting on the resistivity and sensitivity of the earphones connected, this may well be vital. If sensitivity is low and/or the earpiece resistivity is considerably completely different than the supply impedance, a high level output may well be required to atone for the load loss and to urge usable pressure level. If the desired level is higher than the utmost output level of the electro-acoustic transducer electronic equipment, the audio signal are distorted and will cause injury to the earphones. exploitation Associate in Nursing external battery operated electro-acoustic transducer electronic equipment could solve this drawback.

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