• Equal loudness contours (Fletcher&Munson)

    The equal loudness contours (often referred to as Fletcher & Munson contours for reason explained below) represent the level that different frequencies need to have in order to be perceived by a listener as having equal loudness. These curves are measured at different perceived loudness levels (phones). Phones are the same as dB SPLs for 1000 Hz, whereas for other frequencies we'll need to apply gain or attenuation for the ear to perceive the different frequencies as being equal in level.

    At low listening levels, the ear has a hard time hearing very low frequencies, and, to a lesser extent, high frequencies as well. As we go up in level, the differences between frequencies even out. We could say the ear's frequency response is "flatter" at high levels than at lower ones. For example, a 50 Hz 60 dB SPL sinewave will be perceived as being some 10 dB lower than a 1000 Hz sinewave with the same SPL. However, a 50 Hz 100 dB sinewave will only be perceived as being some 10 dB lower than a 1000 Hz one of the same SPL.

    The psycoacoustical phenomena of the different sensitivity of the ear to different frequencies and the variation of that "frequency response" (in fact, the contours are like frequency responses of the ear upside down) with changing listening levels was first thoroughly quantified by researchers Fletcher & Munson in the 1930s. Thus, this type of curves are commonly referred to as Fletcher & Munson contours, although these days more up to date and accurate versions are used, such as those by Robertson & Dadson (shown below), or the standards organization ISO.

    Based on this type of contours are the A, B and C frequency weightings, which correspond to low, mid and high listening levels, respectively, and are used to better correlate microphone level readings with human perception.

    Related reading »» Frequency weightings: A, B and C
  • Ad

  • News

    inMusic acquires ArKaos

    Fort Lauderdale, FL USA (October 27, 2020) inMusic, the has announced the acquisition of ArKaos.

    Founded in 1996, ArKaos specializes in video processing technologies,... Read more

    Meyer Sound launches Spacemap Go, a tool for spatial sound design and mixing

    Meyer Sound has officially released Spacemap® Go for spatial sound design and mixing. Available now as a free app for Apple iPad (any iPad capable of running the latest iPadOS), Spacemap... Read more

    Bose unveils L1 Pro family

    These three new portable Bose PA systems are designed to give artists choices, suit different styles and audiences, and provide an solution for creators reintroducing live music and sound experiences into venues and online platforms across... Read more

    ClearOne BMA 360 beamforming microphone array ceiling tile

    ClearOne (NASDAQ:CLRO), provider of audio and visual communication solutions, has announced its new BMA 360, reportedly the world’s most technologically advanced Beamforming Microphone Array Ceiling Tile.

    The ClearOne BMA 360 is the world’s first truly wideband,... Read more
  • Recent articles

    Power amplifier modes : stereo, parallel and bridge mono

    In general, two-channel power amplifiers for professional use default to stereo mode. That is, each amplifier channel receives a signal from its input connector and its volume is controlled by... Read more

    Basic electricity formulas

    Although it not specific to sound, we include this document with some basic electricity formulas. They can be found in any electricity textbook, but we have added them to the DoPA Library for reference.

    Ohm's law

    The most basic formulas derive from Ohm's law, which specifies that the electric current between two points is proportional to the potential difference (voltage) between them and inversely proportional to the resistance between them. The formula is:
    I = ———

    where I is the current (intensity) in amps and V is the voltage in volts. Since we use alternating current in audio, we have replaced resistance with impedance (Z, and this could also be resistance R), measured in ohms. Clearing Z and V we have these other two formulas:

    Z = ———
    ... Read more

    Y-cables, looping audio signals through

    This article will explain loop-though connections and "y-cables" for analog audio signals.

    To obtain one or more copies of a signal (for example, to distribute the signal from a mixer to various self-powered speakers or power amplifiers) we use parallel connections. To do this we simply connect each terminal (pin) of the connectors in parallel. That is, 1 to 1, 2 to 2 and 3 to 3 (or tip to tip, ring to ring and sleeve to sleeve in a TRS connector). When we split a signal in two in this way, we refer to a "Y-cable" or "Y" connection, since the division of a signal in two looks like letter "y". Contrary to what it may seem, a y-cable is not a technically incorrect solution, but a correct way of splitting the audio signal. In fact, when a self-powered loudspeaker system or one channel of... Read more
  • PAcalculate app