Lambdoma Critical Listening Room DesignIr. Dr. James WongAllied Environmental Consultants Limited, Hong Kong

What is a Critical Listening Room?

We often listen to recorded sound in small spaces. We listen to music, and watch television and movies, in both stereo and surround, in rooms that are much smaller that the recording environments.

If one wishes to evaluate the sound in these environments then it is necessary to make them suitable for this purpose.

Loudspeaker arrangements for critical listening

Loudspeaker arrangements for critical listening

Before we examine specific room designs, let us first examine the optimum speaker layouts for both stereo and 5.1 surround systems.

The reason for doing this is that most modern room designs for critical listening need to know where the speakers will be in order to be designed.

It is also pretty pointless having a wonderful room if the speakers are not in an optimum arrangement.

Optimum stereo speakers layoutThey should form an equilateral triangle with the center of the listening position.

Typical speaker layout for 5.1 surround

5.1 surround

Center dialog speaker: The dialog is replayed via a central speaker because this has been found to give better speech intelligibility over a stereo presentation. Interestingly the fact that the speech is not in stereo is not noticeable because the visual cue dominates so that we hear the sound coming from the person speaking on the screen even if their sound is coming from a different direction.

Surround speakers: The ambient sounds, and sound effects, are diffused via rear mounted speakers. However they are, in the main, not supposed to provide directional effects and so are often deliberately designed, and fed signals, to minimize their correlation with each other and the front speakers. The effect of this is to fool the hearing system into perceiving the sound as all around with no specific direction.

Low-frequency effects: This is required because many of the sound effects used in film and video, such as explosions and punches, have substantial low-frequency and subsonic content. Thus, a specialized speaker is needed to reproduce these sounds properly. Note: this speaker was never intended to reproduce music signals, notwithstanding their presence in many surround music systems.

More recently systems using six or more channels have also been proposed and implemented.

IEC listening rooms(The International Electrotechnical Commission is the international standards and conformity assessment body for all fields of electrotechnology)

The first type of critical listening room is the IEC listening room (IEC, 2003). This is essentially a conventional room that meets certain minimum requirements: a reverberation time that is flat, and between 0.3 and 0.6 seconds above 200 Hz, a low noise level, an even mode distribution and a recommended floor area.

IEC listening roomThe listening room is designed  in accordance with the IEC 268-13 standard and is suitable for subjective evaluations of reproduced sounds from loudspeakers.

The room provides standard listening conditions in which audiovisual equipment, hi-fi systems, loudspeakers or recordings can be assessed subjectively. The acoustics are similar to those of a living room in a house rather than the ‘deadness’ of an anechoic room.

However, for critically listening to music mixes, etc. something more is required and these types of room

Control reverberation.

Control the time evolution and level of early reflections.

Take advantage of the fact that the speakers are in specific locations to do this and very often have an asymmetric acoustic that is different for the listener and the loudspeakers.

Three basic types:

Reflection controlled rooms,

Non-environment rooms, and

Diffuse reflection rooms.

" An idealized energy" time curveIt has three major features

It has three major features:A gap between the direct sound and first reflections.

The presence of high-level diffuse early reflections, which come to the listener predominantly from the side, that is, lateral early reflections.

A smoothly decaying diffuse reverberant field which has no obvious defects, and no modal behavior, and whose time of decay is appropriate to the style of music being performed.

Reflection-controlled roomsThe effect of a shorter initial time delay gap in the listening room.

Here the first reflection the listener hears is due to the wall in the listening room and not the acoustic space of the sound that has been recorded. Because of the precedence effect this reflection dominates, and the replayed sound is perceived as coming from

a space the size of the listening room, which is clearly undesirable.

Maximizing the initial time delay by suppressing early reflections

Making the sound from the loudspeakers appear as if it is coming from a larger space by suppressing the early reflections from the nearby walls

ACHIEVING A REFLECTION-FREE ZONE USING ABSORPTION

EXAMPLES OF THIS APPROACH ARE: "LIVE END DEAD END" (LEDE) (DAVIES AND DAVIES, 1980), "REFLECTION FREE ZONE" (RFZ) (D'ANTONIO AND KONNERT, 1984), AND CONTROLLED REFLECTION ROOMS (WALKER, 1993, 1998).

Achieving a reflection-free zone using absorption

LEDE / RFZ / CR ROOMS

Controlled reflection room

The effect can also be achieved by using angled or shaped walls

Controlled reflection room for free-standing loudspeakers

Sony Music M1, New York, NY.

REFLECTION-FREE ZONESWORKING OUT WHERE ABSORPTION SHOULD BE PLACED IN A ROOM TO CONTROL EARLY REFLECTIONS.

Non-environment room principles

To minimize the amount of absorption needed one should make the listening area as small as possible because larger reflection free volumes require larger absorption patches.

A non-environment listening room

Proponents of this style of room say that the lack of anything but the direct sound makes it much easier to hear low-level detail in the reproduced audio and provides excellent stereo imaging.

This is almost certainly due to the removal of any conflicting cues in the sound, as the floor reflection has very little effect on the stereo image.

A non-environment room

"The Lab," at the Liverpool Music House

These absorbers can take up a considerable amount of space.

The diffuse reflection room

An other approach to controlling early reflections is not to try to suppress or redirect them, but instead diffuse them. This results in a reduced reflection level but does not absorb them.

The geometry for calculating the intensity of an early reflection from a diffuse surface.

For an ideal scatterer, the intensity of the reflection is given by the product of the equation describing the intensity from the source and the one describing the sound intensity radiated by the diffuser.

Idiffuse reflection = (WSource / 4πrs2) × (2 / 4πrd2) 

A diffuse reflection room

"Studio C," at Blackbird Studio, Nashville.

The fact that the reflections are diffuse also results in an absence of focusing effects away from the optimum listening position and this should result in a more gradual degradation of the listening environment away from the optimum listening position.

Fit for the purpose?

We have examined various techniques for achieving a good acoustic environment for hearing both stereo and multi-channel music.

However, the design of a practical critical listening room requires many detailed considerations regarding room treatment, sound isolation, air conditioning, etc.

Critical listening room for healing/wellness purpose.

Body structure The Effects of Vibration on Body

Body structure The Effects of Vibration on Body

SKELETAL DIGESTIVE MUSCULAR LYMPHATIC ENDOCRINE

NERVOUS CARDIOVASCULAR MALE REPRODUCTIVE FEMALE REPRODUCTIVE URINARY

Body Structure: Resonance phenomenon

NOTES AND FREQUENCIES OF THE ORGANS OF THE BODY

ORGAN FREQUENCY/NOTE

BLOOD 321.9 (E)

ADRENALS 492.8 (B)

KIDNEY 319.88 (Eb)

LIVER 317.83 (Eb)

BLADDER 352 (F)

INTESTINES 281. (C#)

LUNGS 220 (A)

COLON 176 (F)

GALL BLADDER 164.3 (E)

PANCREAS 117.3 (C#)

STOMACH 110 (A)

BRAIN 315.8 (Eb)

FAT CELLS 295.8 (C#)

MUSCLES 324 (E)

BONE 418,3 (Ab)

RESEARCH WITH SINE SOUNDS (1982-1988) By: Barbara HeroRESEARCH WITH SINE SOUNDS (1982-1988) By: Barbara HeroRESEARCH WITH SINE SOUNDS (1982-1988) By: Barbara Hero

FUNCTION OF THE BODY MUSICAL NOTE FREQUENCY (Hz)

Personality C+ 264

Circulation,Sex C# 586

Adrenals,Thyroid & Parathyroid B 492

Kidney E 330

Liver Ab 198

Bladder F# 352

Small Intestine C# 281.6

Lungs A 220

Colon F# 176

Gall Bladder E 330

Pancreas C# 117.3

Stomach A 110

Spleen B 492

BODY STRUCTURE: RESONANCE PHENOMENONENDOCRINE SYSTEM

REVERSE ENGINEERING THE GEOMETRY OF HUMAN BODYTHE BASIC HARMONIC FRAMEWORK OF THE BODY USING THE PHYSICS OF A CIRCULAR

IF WE TAKE THE RADIUS OF THE CIRCLE TO BE 2Π AND THEN ALIGN ONE FULL CYCLE OF A HARMONIC STANDING WAVE WITH THE NAVEL, THE FIFTH HARMONIC (A 3:2 PROPORTION) CAN BE FOUND TO MATCH THE CURVATURE OF THE HUMAN SPINE. MORE AMAZING THAN THIS, THE LOCATION AND SPACING OF THE SEVEN TONES OF A MUSICAL MAJOR SCALE ALIGN WITH THE SEVEN HINDU CHAKRA LOCATIONS IN THE BODY.

BY: RICHARD MERRICK

REVERSE ENGINEERING THE GEOMETRY OF HUMAN BODYEMBRYONIC GEOMETRY AS HARMONIC INTERFERENCE PATTERN BETWEEN A SPIRAL AND A CIRCLE

The Tiller Model

Dr. William Tiller, a professor emeritus and researcher at the Stanford Department of Material Science, offers the following model:

FUNCTION <===> STRUCTURE <===> POSITIVE TIME-SPACE ENERGIES (PHYSICAL BODY) <===> NEGATIVE TIME-SPACE ENERGIES (THE ETHERIC BODY) <===> MIND <===> SPIRIT <===> DIVINE

BREAKTHROUGHS IN UNDERSTANDING THE ENIGMABARBARA HERO’S RESEARCH IN LAMBDOMA AND FREQUENCIES

CHAKRA ENERGY CENTERS OF OUR BODIESBARBARA HERO’S RESEARCH IN LAMBDOMA AND FREQUENCIES

CHAKRA ENERGY CENTERS OF OUR BODIESCHAKRA ENERGY CENTERS OF OUR BODIES

CHAKRA FREQUENCY/MUSICAL NOTETRANSPERSONAL 273(1:15)C#(EARTH ORBIT 272)

CROWN 480(15:1)B

unknown 445(1:9)Bb (VENUS ORBIT 442)

THIRD EYE 448(14:1)A

PSYCHIC CENTER 416(13:1)Ab (URANUS ORBIT 415)

unknown 410(1:10)Ab-(VENUS SPIN 409)

unknown 372(1:11)G#(EARTH SPIN 378)

THROAT 384(12:1)G

THYMUS 352(11:1)F#

HEART 341(1:12)F

SOLAR PLEXUS 320(10:1)Eb

DIAPHRAGM 315(1:13)D#

unknown 293(1:14)D+(SATURN ORBIT 296)

POLARITY 288(9:1)D (MARS ORBIT 289)

ROOT 256(1:1)C

ROOM DIMENSIONS AND WAVELENGTHS OF SOUNDBARBARA HERO’S RESEARCH IN LAMBDOMA AND FREQUENCIES

CHAKRA ROOM RESONANCES by Barbara HeroCHAKRA ROOM RESONANCES by Barbara HeroCHAKRA ROOM RESONANCES by Barbara HeroCHAKRA ROOM RESONANCES by Barbara Hero

CHAKRAS NOTE/FREQ ROOM SIZE FEET MIDDLE OCTAVE

ROOT C (126 cps) 9, 18, 36, 72, 144, 288 (252 cps)

POLARITY D (283 cps) 4, 8, 16, 32, 128, 256 (283 cps)

DIAPHRAGM D# (75 cps) 15, 30, 60, 120, 240, 480 (300 cps)

SOLAR PLEXUS E (161 cps) 7, 14, 28, 56, 112, 224 (322 cps)

HEART F (87 cps) 13, 26, 52, 104, 208, 416 (348 cps)

THROAT G (188 cps) 6, 12, 24, 48, 96, 192, 384 (376 cps)

VENUSIAN G+ (49 cps) 23, 46, 92, 184, 368, 736 (392 cps)

GAIA (EARTH) G# (54 cps) 21, 42, 84, 168, 336, 672 (432 cps)

PSYCHIC CENTER Ab (103 cps) 11, 22, 44, 88, 176, 352 (412 cps)

THIRD EYE Bb (113 cps) 10, 20, 40, 80, 160, 320 (452 cps)

CROWN B (59 cps) 19, 38, 76, 152, 204, 408 (472 cps)

TRANSPERSONAL C# (66 cps) 17, 34, 68, 136, 272, 554 (264 cps)

DIAPHRAGM2 D# (39 cps) 29, 58, 116, 232, 464, 928 (312 cps)

POLARITY2 D+ (36 cps) 31, 62, 124, 248, 496, 992 (288 cps)

CROWN B (30 cps) 37, 74, 148, 296, 592, 1184 (480 cps)

Subtle BodiesDr. Gerber's Updated Edition of "Vibrational Medicine, New Choices for Healing Ourselves"

From an energetic standpoint, the human body, when weakened or shifted from equilibrium, oscillates at a different and less harmonious frequency than when healthy.

This abnormal frequency reflects a general state of cellular energetic imbalance within the physical body. When a weakened individual is unable to shift their energetic mode to the needed frequency a certain amount of subtle energetic help may be needed.

When supplied with a dose of the needed energetic frequency, it allows the cellular bioenergetic systems to resonate in the proper vibrational mode, thereby throwing off the toxicities of the illness.

Energy disturbances in the etheric (subtle) body precede the manifestation of illness in the physical body.

The Heart ChakraIt is the center for unconditional love, tolerance, empathy, forgiveness, and compassion. It is the seat of the soul.

The Heart, or Fourth Chakra, governs life lessons involving love and compassion, self confidence and self acceptance, inspiration and hope, generosity, and on the flip side, feelings of despair, hate, envy, fear, jealousy, and anger.

Information stored in the Heart Chakra includes the connections or "heart strings" to those we love.

An imbalance in the Heart Chakra may be felt as a lack of self discipline, difficulty in relationships, attempts to live vicariously through others, and depending on someone else for your happiness.

Calculation of the  Speed of Sound c in Air and the effective Temperature

The important Air Temperature and the non-relevant Atmospheric pressure (Air pressure)

At 0°C is ρ0 = 1.293 kg/m3, Z0 = 428 N·s/m3, and c0 = 331 m/s

At 15°C is ρ15 = 1.225 kg/m3, Z15 = 417 N·s/m3, and c15 = 340 m/s

At 20°C is ρ20 = 1.204 kg/m3, Z20 = 413 N·s/m3, and c20 = 343 m/s

At 25°C is ρ25 = 1.184 kg/m3, Z25 = 410 N·s/m3, and c25 = 346 m/s

Air density or density of air ρ, air impedance Z, speed of sound c

The speed of sound in air is determined by the air itself and is not dependent upon the amplitude, frequency, or wavelength of the sound.

Heart Chakra /Seal Lambdoma Dimensions

1 foot = 0.3048 meters

c 15, air temperature at 15°C, speed of sound at sea level = 340 m / s

speed of sound = frequency x wavelength

Heart Chakra Resonance - 341 Hz

UNITS/DIMENSION NOTE/FREQ ROOM SIZE MIDDLE OCTAVE

Imperial F (87 cps)13, 26, 52, 104, 208, 416 (feet) (348 cps)

S.I. F (87 Hz)

7.92, 15.85, 31.70, 63.40,

126.80, 253.59 (meters)

(348 Hz)/0.98m

Speed of Sound cRoom Air Temperature

(°C) Wavelength (m)

343 20 1.006

346 25 1.014

Lambdoma Dimensions for Heart Chakra/Seal Air Temperature 20°C - 25°C, 341 Hz / 1.006 m -

1.014m, say 1.01m (in meters)

1.01 0.50 0.34 0.25 0.20 0.17 0.14 0.13

2.01 1.01 0.67 0.50 0.40 0.34 0.29 0.25

3.02 1.51 1.01 0.75 0.60 0.50 0.43 0.38

4.02 2.01 1.34 1.01 0.80 0.67 0.57 0.50

5.03 2.52 1.68 1.26 1.01 0.84 0.72 0.63

6.04 3.02 2.01 1.51 1.21 1.01 0.86 0.75

7.04 3.52 2.35 1.76 1.41 1.17 1.01 0.88

8.05 4.02 2.68 2.01 1.61 1.34 1.15 1.01

Lambdoma Critical Listening Room DesignControlled Reflection approach.

Sound sources: Lambdoma frequencies.

Maximize body exposure to direct sound fields.

Adjustable control reverberation.

Control the time evolution and level of early reflections.

Take advantage of the fact that the speakers are in specific locations to do this and very often have an asymmetric acoustic that is different for the listener and the loudspeakers.

Take advantage of the 1st, 2nd and 3rd reflections (spheres in fractals).

Diffuse and diffract sound waves by Lambdoma dimensions.

A PROJECT IN HONG KONGACOUSTICS, NOISE AND VIBRATION CONTROL DESIGN

THE LAMBDOMA CRITICAL LISTENING ROOMFIT FOR THE PURPOSE: ENTERTAINMENT AND WELLNESS

THE LAMBDOMA CRITICAL LISTENING ROOMCONTRACTOR DRAWING: PLAN

THE LAMBDOMA CRITICAL LISTENING ROOMCONTRACTOR DRAWING: REFLECTED CEILING PLAN

THE LAMBDOMA CRITICAL LISTENING ROOMCONTRACTOR DRAWING: ELEVATION SECTION A-A

THE LAMBDOMA CRITICAL LISTENING ROOMCONTRACTOR DRAWING: AIR CONDITIONING DUCT WORKS WITH SILENCERS

THE LAMBDOMA CRITICAL LISTENING ROOMCONTRACTOR DRAWING: VIBRATION ISOLATOR LOCATIONS

THE LAMBDOMA CRITICAL LISTENING ROOMCONTRACTOR DRAWINGS: VIBRATION ISOLATOR LOCATIONS

THE LAMBDOMA CRITICAL LISTENING ROOMCONTRACTOR DRAWINGS: BACK WALL REFLECTOR DETAILS

THE LAMBDOMA CRITICAL LISTENING ROOMCONTRACTOR DRAWING: ACOUSTICS DOOR ON BACK WALL

THE LAMBDOMA CRITICAL LISTENING ROOMAPRIL, 2009

THE LAMBDOMA CRITICAL LISTENING ROOMOCTOBER, 2009

THE LAMBDOMA CRITICAL LISTENING ROOMFEBURARY, 2010

THE LAMBDOMA CRITICAL LISTENING ROOMFINAL ACOUSTICS TESTING MEASUREMENTS: APRIL, 2010

Thank you.Ir. Dr. James WongAllied Environmental Consultants Limited, Hong Kong