What is proximity effect?

Proximity effect is a bass boost that occurs when a directional microphone (cardioid, supercardioid, hypercardioid or figure-8) is placed very close to a sound source — typically within 30cm. The effect increases low-frequency output by up to 6dB or more per halving of distance. It is used intentionally for a warm, full vocal sound, but can cause muddiness if excessive. Omnidirectional mics do not exhibit proximity effect.

How does microphone sensitivity affect signal level?

Microphone sensitivity (dBV/Pa) tells you how much output voltage the mic produces at a reference SPL of 94dB. A higher (less negative) sensitivity value means a stronger output signal, requiring less preamp gain. A large-diaphragm condenser at -32dBV is much more sensitive than a ribbon mic at -55dBV. This calculator uses that relationship to estimate actual output voltage at any SPL.

How does distance affect SPL at the microphone?

Sound follows the inverse square law: doubling the distance from a point source reduces the SPL by approximately 6dB. Halving the distance increases it by 6dB. So a source at 90dB SPL at 1 metre will produce about 96dB at 50cm and 102dB at 25cm. This makes close-miking very effective for capturing loud, quiet or detailed sources.

How much preamp gain do I need?

The required preamp gain depends on the mic output level and your target recording level (typically -18 dBFS). Dynamic and ribbon microphones often need 50-65dB of gain, while condensers typically need 30-45dB. If your preamp's noise is a concern at high gain settings, use an inline booster or a preamp with a very low equivalent input noise (EIN) rating.

What is noise floor margin?

Noise floor margin is the difference between your microphone's output signal and the inherent noise of the mic and preamp system. A margin of 40dB or more is desirable for clean recordings. If the margin is below 20dB, the noise floor will be audible, especially during quiet passages. Choose a quieter mic or a lower-noise preamp to improve the margin.

Microphone Proximity Calculator — Signal Level, Proximity Effect & Gain

Calculate signal level at the microphone, proximity effect bass boost, recommended preamp gain and noise floor margin from source SPL, mic sensitivity, distance and polar pattern.

Source SPL at 1 m

Sound pressure level of the source at 1 metre (typical: speech 65–75, guitar amp 95–110)

Mic Sensitivity

From mic spec sheet at 94dB SPL (e.g. -38dBV for large condenser, -54dBV for dynamic)

Distance

Distance from mic capsule to the sound source

Pickup Pattern

Microphone polar pattern — affects proximity effect calculation

How We Calculate This

This calculator applies the inverse square law and standard microphone sensitivity equations to model signal levels at any recording distance.

SPL at the Microphone

SPL at mic (dB) = Source SPL − 20 × log₁₀(distance in m)

Source SPL is treated as the level at 1 metre from the source.

Microphone Output Level

Mic output (dBV) = Sensitivity + (SPL at mic − 94)

Sensitivity is specified at 94dB SPL (0dBV reference = 1 Pascal).

Proximity Effect Boost

Boost (dB) = Halvings × dB per halving

Halvings = log₂(reference distance / current distance). Effect is strongest for figure-8 patterns and zero for omnidirectional mics.

Frequently Asked Questions

Last updated: March 2026

All calculations are estimates based on standard formulas. Always verify results for critical applications.