| Deutsche Version |
| • Room Modes - Standing Wave Calculator • Calculating the three room modes or eigenmodes
axial tangential oblique The axial, tangential, and oblique room modes of rectangular homogeneous rooms are computed. Axial room modes hit on two facing surfaces. Tangential room modes hit on four surfaces and oblique room modes include six surfaces crosswise. Thus one can find the optimal room dimensions for home cinemas, control rooms, sound studios, and exercise rooms. The distribution of the modal frequencies should be as homogeneous as possible.
Theory is good, but it shows up: The empty room can be computed marvelously, but afterwards the |
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antinodes | nodes | wavelength | frequency | harmonics | overtones |
| 2 | 1 | λ = 2 L | f0 = c / (2 L) | 1st harmonic | fundamental frequency | |
| 3 | 2 | λ = L | f0 = 2 × c / (2 L) | 2nd harmonic | 1st overtone | |
| 4 | 3 | λ = 2 / 3 × L | f0 = 3 × c / (2 L) | 3rd harmonic | 2nd overtone | |
| k + 1 | k | λ = 2 / k × L | f0 = k × c / (2 L) | k. harmonic | (k - 1). overtone |
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The three graphics above: Courtesy of Brüel & Kjær - Technical Review.
To calculate the frequencies of the axial, oblique und tangential modes, use the following formula: ![]() f = Frequency of the mode in Hz c = Speed of sound 343 m/s at 20 °C (68 °F) nx = Order of the mode of the room length ny = Order of the mode of the room width nz = Order of the mode of the room height L, B, H = Length, width, and height of the room in meters The number of modes per frequency width Δ f and even more per frequency interval of Δ f / f increases with rising frequency. Problems with inhomogeneities through in the spectrum clearly separated natural oscillations arise thus particularly in small rooms and at low frequencies. Eigenoscillations arise not only in rectangular rooms, but also in skew rooms. They can be determined there however no longer as simply as here computed, but must be calculated by numeric procedures. An even mode distribution over the frequencies can be reached only by favorable room proportions, especially the eigenfrequencies of different room dimensions should not fall together. Favorable distributions result for proportions (standardized H = 1 on the height) like: (H/B/L).
There is no room correction by setting EQ. You are doing only loudspeaker frequency response correction. EQ systems are not normally used to create a perfect inversion of the room's response because a perfect correction would only be valid at the location where it was measured. A few centimeters away the arrival times from various reflections will differ and the inversion will be imperfect. The imperfectly corrected signal may end up sounding worse than the uncorrected signal because the acausal filters used in digital room correction may cause pre-echo. |

Measurement of a loudspeaker in a room and correction by a parametric equalizer.
| An equalization can not substitute for good acoustics. |
Standing waves in strings, and room modes between hard parallel walls
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