What Is Microphone Sensitivity? An In-Depth Description

You may notice some microphones require more preamp gain than others to achieve the same amount of signal. In other words, some microphones are less sensitive than others.

What exactly is microphone sensitivity? Microphone sensitivity is a measurement of a microphone's efficiency as a transducer (how well it converts acoustical energy to electrical energy). A microphone's sensitivity rating is determined by its output voltage (audio signal strength) relative to the sound pressure level it is subjected to.

Whether we want a high sensitivity or low sensitivity microphone depends on the situation. On the surface, microphone sensitivity seems like a straightforward concept, but there's more to it than meets the eye (or ear). This article details what microphone sensitivity is and why it's a significant factor to consider when choosing the proper microphone for a job!

Related article: The Complete Guide To Headphones Sensitivity Ratings

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Table Of Contents

• What Is Microphone Sensitivity And Why Does It Matter?
• What Microphone Sensitivity Isn't
• What Determines Microphone Sensitivity?
• How Do Manufacturers Calculate Microphone Sensitivity?
• Practical Applications Of Low And High Sensitivity Microphones
• Related Questions

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What Is Microphone Sensitivity And Why Does It Matter?

Simply put, microphone sensitivity is the amount of output for a given input.

The input is the sound pressure level at the microphone diaphragm. A standard 1 kHz tone is used with a sound pressure level of 94 dB SPL or 1 Pascal when measuring microphone sensitivity.

The output is the mic signal, which is an AC electrical signal. The mic output is measured in either mV (millivolts) or dBV (decibels relative to 1 Volt).

All microphones are transducers, meaning they convert one form of energy to another. In the case of microphones, mechanical wave energy is converted into electrical energy.

For more information on microphone transducers, check out the following My New Microphone articles:
• Microphone Types: The 2 Primary Transducer Types + 5 Subtypes.
• What Is The Difference Between Sound And Audio?

The varying sound pressure in the air around a microphone's diaphragm causes it to move (mechanical wave energy). The microphone converts the movement of its diaphragm into an audio signal (electrical energy).

So we have different forms of energy at a microphone's input and output. In terms of microphone sensitivity, they are as follows:

• The microphone input is the sound pressure level at the diaphragm (measured in dB SPL or Pa).
• The microphone output is the voltage across its output connection (measured in mV or dBV).

Let's define the above units of measurement quickly:

• dB SPL are decibels of sound pressure level referenced against the threshold of human hearing (0 dB SPL).
• Pa are Pascals, an SI unit of pressure measurement equal to one newton per square meter.
• mV are millivolts or thousandths of a volt. Audio signals are AC voltages measured as mV RMS (root mean square voltage levels).
• dBV are decibels as referenced to 1 volt.

To learn more on the complex topic of decibels, check out my article What Are Decibels? The Ultimate dB Guide For Audio & Sound.

Why Does Microphone Sensitivity Matter To Audio Engineers?

Microphone sensitivity is important to know how much audio signal we should expect out of our microphones.

Low-sensitivity microphones are preferred when attempting to capture a loud sound source without capturing extraneous sounds.

However, these microphones may not give us enough output when recording quiet sounds. Too much preamp gain applied to a low sensitivity mic increases the ambient sound and introduces preamp noise, which worsens the signal-to-noise ratio and degrades the audio signal.

High-sensitivity microphones are critical for capturing quiet, nuanced, and/or far away sounds.

However, these microphones may be “too hot” to capture loud sound sources. Although mutually exclusive, the maximum sound pressure level is typically much lower in high-sensitivity mics than in low-sensitivity mics.

Active Vs. Passive Microphone Sensitivity

Generally speaking, active microphones have much great sensitivity ratings than their passive counterparts.

Active microphone diaphragms are not necessarily more sensitive to sound than passive mic diaphragms. Rather, the greater sensitivity of active mics is due to the amplification within the mic before the mic output.

• Passive ribbon microphones are generally the least sensitive with sensitivity ratings in the range of 0.5-6 mV/Pa.
• Moving-coil (passive) microphones have typical sensitivity ratings between 1-6 mV/Pa.
• Active ribbon and condenser microphones vary greatly in their sensitivity. The typical range is between 8 and 32 mV/Pa.

Let's take Royer's R-121 passive ribbon mic and R-122 active ribbon mic as an example:

The passive R-121 has a low sensitivity rating of -47 dBV/Pa or 4.5 mV/Pa.

The active R-122 has a high sensitivity rating of -36 dBV/Pa or 15.8 mV/Pa.

The Royer R-121 is featured in My New Microphone's 50 Best Microphones Of All Time (With Alternate Versions & Clones).

To learn more about active and passive microphones, check out my article Do Microphones Need Power To Function Properly?

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What Microphone Sensitivity Isn't

Let's clear up some confusion while providing some insight!

• Microphone sensitivity is not adjustable
• Microphone sensitivity is not the fragility or reactivity of the microphone diaphragm

Microphone Sensitivity Is Not Adjustable

Changing the volume of a microphone is not the same as adjusting a microphone's sensitivity.

Microphone sensitivity remains the same, outputting a certain signal when subjected to a given sound pressure level.

The caveat here is in multi-pattern microphones. When switching between polar patterns in a multi-pattern mic, some specifications change, including sensitivity!

Windows OS would have us believe that microphone sensitivity is alterable. The “sensitivity” of the microphone in the Windows OS control panel actually adjusts gain and not mic sensitivity.

Microphone Sensitivity Is Not The Fragility Or Reactivity Of The Diaphragm

The word “sensitive” is often synonymous with “fragile” or “reactive.” In microphones, they are all independent terms.

The fragility of the microphone diaphragm has nothing to do with its sensitivity rating. The amount of trauma a diaphragm can handle before breaking is mutually exclusive from how efficiently the microphone converts acoustic sound into electrical current.

For example, a ribbon diaphragm is very fragile, so we may assume it would also be “sensitive.” However, passive dynamic ribbon microphones are generally the least sensitive transducer types (compared to moving-coil dynamics and active ribbon and condenser mics).

The reactivity of the microphone diaphragm plays a big role in the conversion of energy in a microphone. However, its role is more centred in determining the quality of the signal (frequency response, transient response, etc.). The reactivity of the diaphragm is not a big factor in determining microphone sensitivity.

Again, let's refer to the ribbon diaphragm as an example. Ribbon diaphragms are arguably more reactive than condenser and moving-coil diaphragms. However, ribbon microphones generally have the lowest sensitivity ratings.

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What Determines Microphone Sensitivity?

Microphone sensitivity, as a specification, is determined by the effectiveness of the microphone as a transducer.

There are three critical processes in the conversion of energy within a microphone that affect the microphone's sensitivity:

1. The reactiveness of the diaphragm to varying sound pressure levels
2. The transducer type and its efficiency
3. The amplification of the audio signal within the microphone

The two most common microphone transducer types are the dynamic microphone and the condenser microphone. However, we can further specialize these microphones into three categories:

• Moving-coil dynamic microphones
• Dynamic ribbon microphones
• Condenser microphones

Let's touch on each of these specialized transducer types and discuss their typical sensitivity ratings:

Moving-Coil Dynamic Microphone Sensitivity

Dynamic microphones work on the principle of electromagnetism.

A moving-coil/dynamic mic capsule is made of a coil of copper wire attached to a movable diaphragm in a magnetic field. As the copper wire moves back and forth through the magnetic field, an AC voltage (audio signal) is produced across it.

The diaphragm/coil combination is heavy and not as reactive as the diaphragms of the other microphone types.

The voltage created across the coil due to electromagnetic induction is minuscule. A step-up transformer is a passive device often used to increase the output of the moving coil dynamic mic.

However, even high-quality step-up transformers can only increase the audio signal so much. Overdoing the “stepping-up” will cause distortion; and a worsening of frequency response. It will increase the microphone output impedance to unwanted levels.

Typical sensitivity specs for dynamic microphones are:

• 1 to 6 mV/Pa or
• -60 to -44 dBV/Pa

*Specs calculated with a 1 kHz pure tone at the microphone capsule.

The Shure SM7B is also featured in My New Microphone's 50 Best Microphones Of All Time (With Alternate Versions & Clones).

For more information on moving-coil dynamic mics, check out my article Moving-Coil Dynamic Microphones: The In-Depth Guide.

Dynamic Ribbon Microphone Sensitivity

Ribbon microphones are usually less sensitive than their moving-coil dynamic counterparts.

A ribbon mic's baffle (capsule) is made of a thin corrugated aluminum ribbon diaphragm suspended between two magnets. Varying sound pressure moves the ribbon back and forth through the magnetic field, causing an AC voltage (audio signal) to be produced across it.

Ribbons are extremely fragile. As we discussed, diaphragm fragility and microphone sensitivity are two separate characteristics.

The voltage created across the ribbon due to electromagnetic induction is minuscule. There are two classes of ribbon microphones, and each of them has its own way of increasing this minuscule voltage to a workable level.

• Passive ribbon microphones utilize passive step-up transformers to increase their output voltage.
• Active ribbon microphones utilize active electronics (including an amplifier) to increase their output voltage.

Typical sensitivity specs for passive ribbon microphones are:

• 0.5 to 6 mV/Pa or
• -60 to -44 dBV/Pa

*Specs calculated with a 1 kHz pure tone at the microphone capsule.

The Coles 4038 is featured in My New Microphone's 50 Best Microphones Of All Time (With Alternate Versions & Clones).

Typical sensitivity specs for active ribbon microphones are:

• 8 to 32 mV/Pa or
• -42 to -30 dBV/Pa

*Specs calculated with a 1 kHz pure tone at the microphone capsule.

For more information on dynamic ribbon mics, check out my article Dynamic Ribbon Microphones: The In-Depth Guide.

Condenser Microphone Sensitivity

Condenser microphones work on the electrostatic principle.

A true condenser microphone capsule is made of two parallel conductive plates that form a capacitor: One stationary backplate and one thin moveable diaphragm. The plates hold a charge via external DC voltage or permanently via electret material.

As the diaphragm moves in reaction to varying sound pressure, the gap between plates changes and, therefore, the capacitance changes. The proportional relationship between capacitance and voltage causes a fluctuation in the output AC voltage (audio signal).

The tightly stretched diaphragm plate is perhaps more sensitive to sound pressure than a dynamic moving-coil diaphragm, but the output voltage is still low.

Condenser microphones utilize active electronics, including an amplifier, to increase the output voltage from the capacitor diaphragm before the microphone's final output.

Typical sensitivity specs for condenser microphones are:

• 8 to 32 mV/Pa or
• -42 to -30 dBV/Pa

*Specs calculated with a 1 kHz pure tone at the microphone capsule.

The Rode NT1-A is also featured in My New Microphone's 50 Best Microphones Of All Time (With Alternate Versions & Clones).

High-Impedance Microphones

No professional mics are considered high-impedance. However, I thought I'd mention them here to further our understanding of microphone sensitivity as it relates to microphone impedance.

The higher the impedance, the higher the output signal voltage. However, the many disadvantages of high-output-impedance microphones keep them out of professional scenarios.

With consumer-grade (think karaoke) microphones, high output impedance (and therefore high sensitivity) allows the mics to be made inexpensively. There's no need for sophisticated amplifiers! Of course, this is all at the expense of poor audio quality.

For an in-depth read on microphone impedance, check out my article Microphone Impedance: What Is It And Why Is It Important?

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How Do Manufacturers Calculate Microphone Sensitivity?

The industry-standard test of a microphone's sensitivity involves producing a 94 dB SPL, 1,000 Hz (1 kHz) pure tone (sine wave) at the mic capsule and calculating the resulting output.

Let's recap that in bullet form:

• 1 kHz (1000 Hz) pure tone
• 94 dB SPL (equal to 1 Pascal or 10 microbars)
• At the microphone's capsule (no loss of acoustic energy before the tone hits the microphone)

The microphone will output an AC voltage in response to the air vibration created by this tone (input).

The sensitivity of the microphone is then expressed as the resulting voltage across its output connection.

Open Circuit Output Voltage And Bridging Impedances

Assumptions are made when calculating the sensitivity of a microphone.

• The load impedance of a professional microphone will be much greater than its output impedance
• There will be maximal voltage transfer between the microphone and mic preamp
• Therefore, the open circuit microphone output voltage is a useful measurement

Impedance bridging happens when the microphone output impedance is much lower (typically at least 10x less) than the input impedance of the mic preamp.

Bridging allows for maximal voltage transfer between the mic output and the preamp input. In fact, we can call this voltage loss negligible.

Maximal voltage transfer or minimal voltage loss means that open-circuit output voltage is a meaningful specification for microphones. The open-circuit output voltage is practically the same voltage that should be transferred to a bridged mic preamp!

European Vs. American Sensitivity

As with many simple ideas, there are always ways to complicate them. These complications often stem from the lack of a global standard.

American and European microphone manufacturers typically note sensitivity specs differently on their respective mic spec sheets.

Thankfully they both use the same reference tone mentioned earlier in the article:

A 1 kHz tone @ 94 dB SPL or 1 Pascal

European Sensitivity

European sensitivity (sometimes called “transfer factor”) is measured and specified as millivolts per pascal.

More specifically, the transfer factor answers “how many mV per Pascal @ 1 kHz tone (at the mic capsule)?”

This is perfectly logical with regards to the way sensitivity is tested: send a 1 Pascal (94 dB SPL) 1 kHz tone at the microphone capsule and measure the produced output voltage.

However, output voltage per Pascal is tricky when comparing the sensitivity of two microphones.

American Sensitivity

American mic manufacturers, in my opinion, make it easier to compare microphones and estimate the required gain a microphone will need in the preamplifier stage.

They specify the sensitivity of the microphone in dBV (decibels relative to 1 volt).

In other words, American manufacturers relate their mics to a hypothetical microphone (so right off the bat, there's a comparison). This hypothetical mic outputs 1 volt when subjected to the 1 Pascal (94 dB SPL) tone and is much “hotter” than any actual microphone on the market.

Microphone sensitivity rating is based on how quiet a mic is compared to this “one-volt mic.” The rating is given as a negative dBV value per Pascal.

More specifically, the microphone sensitivity spec answers “how many dBV per Pascal @ 1 kHz tone (at the mic capsule)?”

A mic with a −40 dBV/Pa sensitivity rating is 10 dB more sensitive than a mic with a −50 dBV/Pa rating.

Many microphone companies have adopted all of the above units. This makes for a long specification but provides all the “standardized” info we could need.

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What Is A Good Microphone Sensitivity Rating?

What is a good microphone sensitivity rating? A good mic sensitivity rating depends on the application. The lower the sensitivity, the more gain is required to boost the mic signal to line level. At conversation level (70 dB), a 16 mV/Pa mic sensitivity would require 60 dB of gain to reach line level, which could be considered a good rating.

There's no hard-set rule for proper use of low versus high-sensitivity microphones.

As I've mentioned above, a “good” microphone sensitivity rating depends on the application. Let's quickly run through situations where a low-sensitivity mic would excel and other instances where a high-sensitivity microphone would be preferred.

One factor to take into account is the quality of the preamp the microphone is plugged into. Lower sensitivity microphones require more preamp gain. Preamps often add unwanted noise to the microphone signal. So if you decide to use a low sensitivity microphone to capture quiet sources, be wary of the preamp the mic is connected to.

With that being said, it's probably better to use high-sensitivity microphones to capture quiet sources and low-sensitivity microphones to capture loud sources.

Low-Sensitivity Microphone Applications

Low-sensitivity mics (which typically means passive dynamic mics) have very high (often immeasurable) maximum SPL ratings. This makes them excellent choices for close-miking loud sound sources like kick and snare drums, guitar and bass cabinets, and horns.

Pro tip: do not place a ribbon mic (low-sensitivity) directly on-axis in front of a sound source that moves a lot of air. Although the high SPL will not damage the microphone, the large gusts of air could potentially stretch or snap the ribbon!

Low-sensitivity mics are also a good choice for close-miking voices in less-than-deal (non-soundproof) environments. So long as we close-mic the voices and supply the proper amount of gain, low-sensitivity mics can accentuate the voice and pick up as much extraneous noise.

Low sensitivity mics are generally better for:

• Close-miking drums
• Miking guitar and bass guitar amplifiers
• Vocal and horns mics in a loud live band setting
• Recording high SPL sources (such as gunshots)

High-Sensitivity Microphone Applications

High-sensitivity microphones shine in the soundproof rooms of studios around the world. The high sensitivity will pick up the sound source clearly without the need for a lot of gain.

As for ambience or room mics, high-sensitivity mics excel due to their ability to pick up close and distant sounds. Mics with lower sensitivity ratings will often lose that clarity of distance and quiet sounds.

High-sensitivity mics are also great as shotgun mics in film (combined with the highly directional polar pattern).

Similarly, high-sensitivity mics are used in parabolic systems to capture sound long distances away with clarity.

High sensitivity mics are generally better for:

• Voice-over work
• Recording ambience and natural sound
• Parabolic microphone setups
• Long-distance “shotgun mic” recording
• Recording acoustic guitar
• Room sound microphones

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Related Questions

How can I get more signal out of my microphone?

• Choose a mic with a high sensitivity rating
• Increase the volume of the sound source
• Move the mic closer to the sound source
• Ensure the mic is plugged into a mic input
• Disengage pads on the mic or preamp
• Ensure phantom power requirements are met for true condenser and active ribbon mics
• Increase the preamp gain

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How to convert output voltages to dBV?

dBV = 20 * log₁₀V

where V is the output voltage in volts (rms)

1 Volt (rms) = 0 dbV

Here are some conversions of typical microphone values:

• 1 mV (rms) = −60 dBV 
• 2 mV(rms) = −54 dBV
• 4 mV(rms) = −48 dBV
• 8 mV (rms) = −42 dBV
• 16 mV(rms) = −36 dBV
• 32 mV(rms) = −30 dBV

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How to convert Pascals to dB SPL?

dB SPL = 20 * log₁₀(Pa/(2.0 x 10⁻⁵))

where Pa is the pressure at the diaphragm in Pascals

1 Pascal = 94 dB SPL

2.0 x 10⁻⁵ Pascals is the threshold of human hearing (0 dB SPL)

For information on all the possible microphone specifications, please continue to my article Full List Of Microphone Specifications (How To Read A Spec Sheet).