International Planetarium Society
We study how domes actually sound, publish what we find, and help the people who build, calibrate and mix for them arrive at the same answer.
We hear where we are.
Sound is the first sense that goes into action when we are forming in our mother's womb, and the last sense to go when we die. Our ears do not blink and do not close during sleep.
We hear in all directions. We hear above us and below us. We can tell the distance and size of both a bird and an approaching thunderstorm. In the dark we listen carefully, and we remember well.
In the planetarium, the visuals dominate the senses. But sound is always there, and unlike our visual sense, we cannot turn it off.
From the Sound Experience Survey Report: Fulldome and Planetariums, published by this committee with IMERSA.
We surveyed the field across four roles: creators, technical operators, facility decision makers and producers. Forty-two practitioners answered.
of audio creators say what they most want is more standards.
of facilities have no dedicated sound engineer.
of operators set show volume by ear. One in five uses a meter.
of facility decision makers name cost as the obstacle to better audio.
Half of the domes surveyed run a 5.1 system. Speaker counts range from six to fifty-eight. Every dome is different, so a mix approved in one room is a different show in the next, and nobody can say whose fault that is. That is the problem this committee exists to close.
Every layout puts energy into the room differently. Bright is loud, dark is quiet, and the smoother the picture, the more seats hear the same thing.
Two things. Inform and inspire through listening experiences of the power of immersive sound. And define the requirements on sound and acoustics, and set the standards for healthy sound.
In scope: room acoustics, speech intelligibility, spatial sound quality, music and effects, content exchange, the hardware and software of production and reinforcement, and acoustical immersion.
The same specification means three different things depending on where you sit.
A study with IMERSA of how audio is produced, presented and distributed in domes, published as a state of the industry report in English, German and Spanish. Still open for responses.
A listening kit for evaluating a venue's sound: guided exercises, a structured question set, and plain language for discussing quality with staff and audiences. Mixed in stereo, 5.1 and Dolby Atmos.
A draft, under committee review: one measurable operating point a dome anywhere could be set to, so a mix approved in one venue is the same show in the next.
Shared vocabulary, guided listening, production orientation and a venue self-assessment guide. Tiered, so an educator and a system designer each find their level.
Composers, re-recording mixers, tool builders, venue directors and the engineers who calibrate rooms for a living.
Composer and public sound artist. Founder of MorrowSound, holder of patents in True3D and 360° VR sound.
Immersive audio artist and engineer, founder of Resonant Interactions, IMERSA board member, co-host of the Immersive Audio Podcast.
Founder of New Audio Technology and creator of Spatial Audio Designer, released in 2011 before Dolby Atmos existed.
Astrophysicist, former IPS President and founder of this committee. Commissioned Jean-Michel Jarre and Hans Zimmer for the dome.
Managing director of Primetime Studio. Mixes for the dome in both Dolby Atmos and Fraunhofer SpatialSound Wave.
Multichannel work since the 1980s, fifteen years running a sound art gallery, and time on the wave field synthesis system at TU Berlin.
Decades of film and television mixing, latterly in Dolby Atmos and in binaural for VR.
Sound designer for giant screen film and themed attractions, and principal at Advanced Listening Systems.
Planetarium manager, musician and technician. Brings a working venue's perspective on how festivals recognise immersive sound.
From the institute that developed SpatialSound Wave, installed in a number of European domes.
Twenty years building domes, a decade with Vortex Immersion, now distributing fulldome work to more than a hundred venues worldwide.
For audio creators, mixers and distributors
Half of you mix in your own room on headphones. Only 29% ship a single mix; the rest build several. And three quarters of the time, somebody in the venue adjusts your loudness after you have gone. This is what you can control from where you sit.
A calibrated dome is a theatrical room, and theatrical rooms have a fixed, known playback gain. The room is normalised, so the file does not have to be. That is the opposite of streaming and broadcast, and it is why a loudness target you would use for either will make your dome mix wrong.
The proposed operating point is 85 dB, C-weighted, slow, measured with pink noise in one channel at a time. Most nearfield rooms sit at 79 or 82. That difference is not an error in either room. It means a nearfield mix and a theatrical mix are two separate deliverables, and a dome needs the second one.
Monitor at the level the venue is set to. If your room and the dome share an operating point, what you heard is what the audience hears. Everything downstream gets easier.
Deliver three formats. Binaural, which plays on any headphones and needs nothing installed. 5.1, because half the domes surveyed run one. And one genuinely immersive render at 7.1.4 or above, which plays on a twelve-channel room and a fifty-channel dome alike.
Check the low end on an analyser. The LFE is aligned by in-band gain across its own bandwidth, not by a broadband number. A subwoofer set by ear is almost always hot.
Ask for the calibration report. Two questions when you licence into a venue: was it calibrated, and when was it last verified. You will not get an answer everywhere, and that is itself the answer.
For system designers, installers and calibration engineers
Every facility decision maker we surveyed named cost as the obstacle to better dome audio. More than half named technical knowledge. Their upgrade budgets sit between fifty and a hundred thousand dollars. You are the only person in the chain who decides whether that money lands well.
The calibration target constrains the design, not the other way round. The draft reference level is 85 dB C-weighted with about 20 dB of headroom above it, so every main channel has to be capable of 105 dB SPL at the reference position and the subwoofer array 110 dB. Specify backwards from that figure and the system either reaches it or it does not.
Two conditions gate everything else: background noise below NC 25, and reverberation time around half a second at 500 Hz. The giant screen community already holds domes to a noise floor stricter than first-run cinema. A system that meets its own numbers in a room that misses these will be described by the client as a speaker problem.
In a rectangular room, loudspeakers sit at roughly equal distances from the audience. In a dome they sit on the spring line or behind a perforated screen, at markedly different distances from the centre of the room. Where drivers do not lie on a common sphere, align them at the central listening position to within 100 microseconds.
No cinema B-chain standard addresses this. It is the defining acoustic difference between a dome and a theatre, and getting it wrong smears every image in the mix while every level reading looks correct.
Measure in at least four places. A dome is a concave focusing surface. One position gives you one correct seat and a room full of wrong ones, which is the exact failure the committee's published specification names first. Keep adding positions until the spread between them settles.
Do not assume the surround offset. The familiar three decibels is derived for two arrays fed the same signal. With a radial array of many zones you are elsewhere, and the standard permits anywhere from one to four decibels depending on speaker count, spacing, room dimensions and reverberation time. A dome pushes all four to the extreme. Measure the summed level.
Verify capability, do not read it off a datasheet. Sensitivity tells you nothing about where a loudspeaker stops behaving linearly. Use a real maximum-output measurement.
Hand over a calibration report. Positions, readings, date. It is the difference between a system you installed and a system the venue can maintain.
For technical operators and venue staff
More than half the facilities we surveyed have no dedicated sound engineer. One in five has nobody who really understands the audio setup. Seven in ten set show volume by ear. If that is your room, none of this is your fault, and all of it is fixable in an afternoon.
Feed pink noise to one main channel with the fader at its reference position. On C-weighting, slow response, it should read 85 dB under the proposed reference level. Switch to A-weighting and it should read about 82. Surround zones sit a few decibels lower.
The gap between those two readings is the useful part. Between 2 and 4 dB means the system is balanced. Outside that, the equalisation is wrong and no level setting will fix it.
Type in what your meter says.
Not when something sounds wrong. By then you are guessing. Put it in the maintenance calendar next to the projector lamp, and keep the numbers.
The log is the point. A record of what the room read last quarter turns "the show sounded off last night" into something somebody can actually find.
A sound level meter, a measurement microphone and free software will find every fault above. Class 1 instruments matter when a number goes into a formal report; for a quarterly health check, a good Class 2 meter and a calibrated USB microphone are enough.
Draft specification
A dome that is not calibrated to a known reference plays everything at a level and a balance the mixer did not intend. Commercial cinema settled this in the 1970s and has held it since. Domes never had it.
In this draft, a dome is correctly calibrated when pink noise fed to one main channel at a time, fader at reference, produces 85 dB SPL, C‑weighted, slow, averaged across the seating area.
A draft under committee review, not an adopted standard. Every value is drawn from a published standard and cites its source. Select a row for the detail and the caveats.
Directory
The software, instruments and documents the field uses. Where something is free, we say so. Where a cheaper option does the job, we say that too.
Listed because practitioners use them. Inclusion is not an endorsement by the International Planetarium Society, and nothing here is a commercial relationship.