The sensitivity rating of a microphone tells us how strong the mic’s output signal will be at a given sound pressure.
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 mic sensitivity of 16 mV/Pa would require 60 dB of gain to reach line level, which could be considered a good rating.
That answer is still very vague. Let’s discuss what makes for a good microphone sensitivity rating in other applications and in general.
For a full list of microphone specifications, check out my article Full List Of Microphone Specifications (How To Read A Spec Sheet).
What Is Microphone Sensitivity?
Before we get into what constitutes a “good” sensitivity rating, let’s break down what microphone sensitivity is.
A microphone sensitivity rating is an indicator of the microphone’s output signal strength per unit of sound pressure.
The output ratings are typically given as millivolts AC (mV) or decibel relative to 1 volt (dBV).
The sound pressure level is typically given in Pascals (Pa) or decibels of sound pressure level (dB SPL), though some older mics have their sound pressure specified in dyne/cm2.
Microphone sensitivity ratings are standardized and measured at a certain SPL with a certain tone. The measurement of the output signal is always measured with:
1 Pascal (94 dB SPL) 1,000 Hz tone at the microphone capsule.
All microphone sensitivity ratings are given as the microphone’s output signal strength (in mV or dBV) when subjected to the tone mentioned above.
Knowing the sensitivity at 1 kHz doesn’t necessarily translate to knowing the mic’s sensitivity across the frequency spectrum. However, it gives us a good idea of what to expect the output signal strength to be.
On top of that, generally speaking, all microphones are sensitive in the 1 kHz range, which helps with standardization.
For more information on microphone sensitivity, check out my article What Is Microphone Sensitivity? An In-Depth Description.
Related article: What Are Decibels? The Ultimate dB Guide For Audio & Sound.
Passive Microphone Sensitivity Ratings
Passive microphones, like moving-coil dynamics and most ribbon mics, have lower sensitivities.
The AC voltage that is outputted from a dynamic microphone cartridge or element is very small. Other than a step-up transformer at the mic output, there is really nothing to boost the signal.
Therefore, passive dynamic mics have relatively low sensitivity ratings:
- Moving-coil dynamic mic sensitivity ratings are generally between 1 to 6 mV/Pa (-60 to -44 dBV/Pa)
- Passive ribbon dynamic mic sensitivity ratings are generally between 0.5 to 6 mV/Pa (-66 to -44 dBV/Pa)
Good passive microphone sensitivity ratings are between this 0.5 mV/Pa to 6 mV/Pa range. The mics at the lower end of this range will need more gain, and therefore rely more heavily on the mic preamp, in order to get boosted to line level (for use in professional audio equipment).
For in-depth information on dynamic microphones, check out the following My New Microphone articles:
• The Complete Guide To Moving-Coil Dynamic Microphones
• The Complete Guide To Ribbon Microphones (With Mic Examples)
Active Microphone Sensitivity Ratings
Active microphones generally have internal amplifiers and are more sensitive than their passive counterparts.
An active microphone (whether a condenser or active ribbon) will typically have a sensitivity rating within the range of 8 to 32 mV/Pa (-42 to -30 dBV/Pa).
Good active microphone sensitivity ratings are between this 8 mV/Pa to 32 mV/Pa range. These mics will still require gain from a preamp in order to get boosted to line level, though not nearly as much as passive mics.
For more information on active and passive microphones, check out my article Do Microphones Need Power To Function Properly?
Getting From Mic Level To Line Level
So far, a lot of emphasis has been put on getting the mic signal to line level for use with professional audio equipment. The lower the microphone sensitivity, the more gain is necessary to make this happen.
Let’s take a closer look at our conversation example in the opening paragraphs.
Conversational level = ~70 dB SPL
Mic sensitivity ratings are measured against a 94 dB SPL tone.
So right from the get-go, we know that the mic preamp would need to supply the mic signal with 24 dB of gain in order to boost our conversation level to the level noted by the mic sensitivity rating.
On top of that, the preamp would need to supply enough gain to bring the mic signal to line level.
Professional line level is notes at +4 dBu which is equal to 1.78 dBV. For simplicity, we’ll round up to 2 dBV as our benchmark for the preamp gain required to boost our mic level (in the mic) to line level (at the preamp).
For more information on microphone gain, check out my article What Is Microphone Gain And How Does It Affect Mic Signals?
Let’s crunch some numbers here:
As an example of a microphone with a high sensitivity rating, let’s look at the Rode NT1-A, which has a sensitivity or 25 mV (-32 dBV)/Pa.
Rode is featured in My New Microphone’s Top 11 Best Microphone Brands You Should Know And Use.
The sensitivity of the Rode NT1-A tells us that at 94 dB SPL, the mic will output -32 dBV.
Therefore, at 70 dB SPL, the mic would output -56 dBV (-32 – 24).
That means that the preamp would need to provide 58 dB of clean gain to bring the NT1-A’s signal to line level. This is easily achievable with any professional preamp worth its salt.
For a medium-sensitivity mic example, let’s look at the original Neumann U 87, which has a sensitivity rating of 8.0 mV (-42 dBV)/Pa.
Neumann is featured in My New Microphone’s Top 11 Best Microphone Brands You Should Know And Use.
The sensitivity of the Neumann U 87 tells us that at 94 dB SPL, the mic will output -42 dBV.
Therefore, at 70 dB SPL, the mic would output -66 dBV (-42 – 24).
That means that the preamp would need to provide 68 dB of clean gain to bring the Neumann U 87’s signal to line level.
There are plenty of mic preamps out there that are capable of supply 68 dB of clean gain (emphasis on “clean”). However, in many cases, we would would be pushing the preamps pretty hard and the gain may start introducing distortion to the signal.
For a low-sensitivity mic example, we’ll discuss the Beyerdynamic M 160, which has a sensitivity rating of 1.0 mV (-60 dBV)/Pa.
The sensitivity of the Beyerdynamic M 160 tells us that at 94 dB SPL, the mic will output -60 dBV.
Therefore, at 70 dB SPL, the mic would output –84 dBV (-60 – 24).
That means that the preamp would need to provide 86 dB of clean gain to bring the Beyerdynamic M 160’s signal to line level.
This is an issue. Many preamps are not capable of supplying this much gain. And even in those preamps that can, there would likely be distortion added to the signal.
So then why are low microphones like the Shure SM7B (1.12 mV/Pa) and Electro-Voice RE20 (1.5 mV/Pa) used to record vocals so often?
Well, much of the time, there is an extra gain stage with these microphones when they’re used at conversational levels. A popular in-line preamp option is the Cloudlifter CL-1 (link to check the price on Amazon), which provides up 25 dB of gain to the mic signal before it hits the main preamp.
For more information on mic level and line level, check out my article Do Microphones Output Mic, Line, Or Instrument Level Signals?
Applications For Different Microphone Sensitivity Ratings
As I’ve mentioned above, a “good” microphone sensitivity rating depends on the application. Let’s quickly run through some situations where a low-sensitivity mic would excel and other instances where a high-sensitivity microphone would be preferred.
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 source 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.
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 ambience or room mics, high-sensitivity mics excel due to their capability to pick up both 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.
How do I lower my mic sensitivity? The sensitivity rating of a microphone is set (unless you alter the microphone components). However, Windows OS refers to mic gain/volume as “sensitivity” and in order to change that value, do the following:
- Open Control Panel.
- Open Sound.
- Click the Recordings Tab.
- Click on Microphone.
- Change the Sensitivity Levels.
What are the characteristics of a good microphone? Although there are many variations between microphones, professional mics typically have the following characteristics:
- Low output impedance.
- Consistent polar response.
- Balanced output.
- Low self-noise.
For in-depth articles on the important microphone characteristics listed above, please read the following My New Microphone articles:
• Microphone Impedance: What Is It And Why Is It Important?
• The Complete Guide To Microphone Polar Patterns
• Do Microphones Output Balanced Or Unbalanced Audio?
• What Is Microphone Self-Noise? (Equivalent Noise Level)