By Full Compass LiveBreaking Down the Basics of Microphone Specs to Help you Buy Smarter
Reading through microphone specifications can be overwhelming and confusing even for the experts. This is a quick guide to help you sift through the specs and figure out what model is best for your purposes.
Keep in mind, a microphone’s specifications are only that – detailed numerical information. Beyond the numbers, certain models will deliver different sonic experiences that may resonate more with each individual user and performer. You want to find a microphone that not only captures the sound accurately, but also inspires a performer to go further and discover more nuances to their delivery.
The Decibel Scale
The decibelDefinition:
Abbreviated as dB. 1. A deciBel is a logarithmic ratio between two quantities, and is a nonlinear measurement that mimics human perception. 2. A unit expressing sound levels relative to a nominal level just audible by the average human ear, and equal to 1/10th of a Bel. (dBDefinition:
1. A deciBel is a logarithmic ratio between two quantities, and is a nonlinear measurement that mimics human perception. 2. A unit expressing sound levels relative to a nominal level just audible by the average human ear, and equal to 1/10th of a Bel.) scale is the starting point for discussing microphone specs. The dB scale serves as the best guide for how the human ear perceives sound pressure changes. It calculates a given pressure in proportion to a reference pressure. For example, 0 dB does not mean zero sound. It simply represents the inability of the human ear to detect sound and pressure changes at that range.
Frequency Response
The frequency responseDefinition:
The range of frequencies that an audio, video or data device can pass. curve grades the microphone’s ability to accurately transform acoustic energy into electrical signals without adding or losing tone or colorationDefinition:
Modification of a video signal's color.. Do not confuse frequency response with frequencyDefinition:
A value, expressed in Hertz, that indicates how many cycles of a periodic signal occur in one second. range (which is often called bandwidthDefinition:
A range of frequencies that a device can generate, reproduce, or process. This usually implies little or no alteration within the range.). Manufacturers of professional equipment will always provide more than one frequency response curve, as it is essential to see how the microphone will respond to sound coming from different directions and in different acoustic sound fields.
On-Axis Response
This specification measures a microphone’s ability to respond to sound coming directly at it, on-axisDefinition:
The direction where a microphone, speaker, or antenna is most sensitive, or radiates the most power., towards its diaphragmDefinition:
The moving portion of a microphone that transforms sound waves into motion that can ultimately produce electrical waves. (0°). It is important to understand that on-axis response may be measured from different distances, which may impact the response because of the proximity effectDefinition:
A phenomenon where most microphones with cardioid or figure-8 polar patterns exaggerate bass frequencies as the sound source moves closer to the microphone. Also called Bass Tip-Up.. Each model should state at which distance the directional microphone has been measured.
Diffuse Field Response
How does the microphone respond in a highly reverberant sound field where the acoustic sound is not coming from a specific direction but from all directions? Imagine sound ricocheting off walls and floors and other surfaces contrasting with a direct soundDefinition:
1. Sound arriving directly from the source, not reflections. 2. When spelled DirectSound, a mostly obsolete native Windows audio driver.. Consider omnidirectionalDefinition:
A pattern describing a microphone, radio antenna, or loudspeaker that radiates or picks up in all directions equally. microphones with their ability to register the full frequency range at lower frequencies. The diffuse field response will demonstrate a microphone’s ability to capture across frequencies within a reverberant environment.
Off-AxisResponses
This measurement is a corollary to On-Axis Response. It measures the microphone's response to sound coming at it from different angles. Off-axisDefinition:
The characteristic of signals coming to, or emanating from, a less-sensitive point of a microphone, speaker, or antenna, or a point that doesn't radiate the most power. For example, sound addressing a microphone outside the angle of maximum pickup is considered off-axis or off-mic. See Axis. coloration can greatly impact your recording, so, if you need a good directional microphone, you’ll want to consider how well the model eliminates sound coming from other angles.
Polar Response
It is important to have smooth and symmetrical gradients of sound levels across frequencies and different angles. A polar diagram uses a reference point to determine the amount of coloration and strength of signal. Extreme peaks and valleys are unwanted and the response curves should not cross each other.
From the polar plotDefinition:
See Polar Pattern., you can also see how omnidirectional microphones usually become more directional at higher frequencies (the bigger the microphone, the more directionality at high frequencies).
Equivalent Noise Levels
Every microphone brings its own “self-noise.” This is called the equivalent noise level – the sound pressure levelDefinition:
A measurement of sound amplitude in the air expressed in decibels, referencing 0 dB SPL = 20 micro Pascals = 0.0002 dynes/cm2. that represents the same voltageDefinition:
Also called electro-motive Force (EMF). The "charge potential" or pressure of electrons that causes current to flow in a circuit. the microphone model actually generates by itself. Ideally, you are looking for the lowest noise level to limit unwanted sound – especially when working at low levels of incoming sound. The self-noise also dictates the lower limitation in the microphone's dynamic rangeDefinition:
1. Range in dB between a device's noise floor and its maximum available headroom. 2. The difference between the maximum and minimum volume levels that occur in a musical performance..
Sensitivity
The sensitivityDefinition:
In transducers and amplifiers, the how much input energy is needed to produce the desired output. of a microphone is the electrical response at its output to a given standard acoustic input. This is expressed as the ratio of the input pressure to the electrical output (voltage or digitalDefinition:
A signal or data expressed as series of the digits 0 and 1, typically represented by values of a physical quantity such as voltage or magnetic polarization. word). The standard reference input signal for microphone sensitivity measurements is a 1 kHzDefinition:
kHz (Kilohertz): 1,000 Hertz, or one thousand cycles per second. sine waveDefinition:
A pure-sounding tone, whose energy is concentrated solely at its fundamental frequency. Commonly used in testing audio devices, and music synthesis. at 94 dB sound pressure level (SPLDefinition:
See Sound Pressure Level.), or 1 pascal (Pa, a measurement of pressure). A microphone with a higher sensitivity value has a higher level output for a fixed acoustic input than a microphone with a lower sensitivity value. Microphone sensitivity in decibels (dB) is typically a negative number; therefore a higher sensitivity is a smaller absolute value.
It is important to note the units presented with the sensitivity specifications of the microphone. It is incorrect to directly compare the sensitivity of two microphones if the sensitivity is not specified for the same unit. For analogDefinition:
A signal that is continuous in nature, as opposed to being defined as a series of discrete numbers (or elements) as found in digital signals; electrically "analogous" to an acoustical signal in the air. microphones, the sensitivity is typically specified in units of dBVDefinition:
A specific type of deciBel whose 0 dBv reference point is 1.0V with an open circuit. -10dBV is a standard level for consumer-grade audio equipment., that is decibels with reference to 1.0 V rms. For digital microphones, the sensitivity is typically specified in dB FS, that is decibels with reference to full-scale digital output (0 dB FS). For digital microphones, a full-scale signal is defined as the highest signal level that can be output from the microphone.
SPL Handling Capability
SPL refers to the Sound Pressure Level that a microphone can handle. It is important to know the SPL at which a certain Total Harmonic DistortionDefinition:
The presence of harmonics at a device's output that are not components of the input signal, and is usually undesirable. (THDDefinition:
(Total Harmonic Distortion) See Harmonic Distortion.) occurs. You want to have a good sense of the limit before the point at which audible distortionDefinition:
A change in an electronic or acoustic signal's waveform. This can undesirable if it impacts signal quality, or desirable when used for creative signal processing. can be detected.
Find the Model You Need Within Your Price Range
It’s not enough to like your mic. We want you to love it. We want you to find a model that you swear by. That you rave about to every performer and producer you know. To help you find your ideal model, shop from a wide assortment of top brands for every budget at Live Sound/Microphones. Or contact one of the Full Compass Sales pros at 800-356-5844 for experienced answers and expert advice.