Title means "Quietness", "Comfortable Sound" and "Excellent Acoustics"

Nagata Acoustics News 00-10 (No.154)
Issued : October 25, 2000

New, Economically-designed, Soundproofed Condominium is a Hot Property

by Akira Ono

The concept of an entire condominium complex designed with soundproofed interiors to attract musicians who want to practice their instruments at home may be a novel idea in many places, but in crowded Japan, these multi-unit dwellings are already commonplace. Typically, when a Japanese condominium is marketed as soundproof, this means that a second, sound-isolating layer was designed into the framework, and that double window frames and doors were installed throughout the structure. These condominiums provide sound isolation performance of D-65 or above, and generally allow residents to play their musical instruments at any time of day or night without disturbing their neighbors. The soundproofing aspects of these condominiums require no special or extra upkeep on the part of the original developer, and individual units maintain their soundproof "value" when they are re-sold or rented to tenants.

<< "Musicians' Kawagoe" Offers a New Approach to Soundproof Condos >>

Recently, Nagata Acoustics served as acoustical consultant for the development of a soundproof condominium complex that differs in several ways from the norm described above. Instead of soundproofing every room for musical practice of any kind, the structure's floor plan locates the living rooms of individual condominiums so that they share a common wall, and assumes that residents will play their musical instruments in their living rooms. The structure's sound isolating functionality is concentrated around and between the living room areas.

As a result of Musicians' Kawagoe's novel approach to soundproof condo design, the living space of the condominium units is maximized. In addition, the developer realized lower development costs, a benefit passed on to tenants through lower rental rates than other soundproof condominiums. One limitation of the new condominium is that the developer set some restrictions on the hours that instruments can be played as well as on which instruments are acceptable. With these limitations in place, the residents of Musicians' Kawagoe live harmoniously and can play their instruments without disturbing their neighbors.

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<< Specifications of Musicians' Kawagoe Condominium Layout >>

Musicians' Kawagoe is an eight-story, reinforced concrete structure. Standard layout floors have 10 units each. The penthouse floor has three units, each of which is twice the size of a standard unit. The total number of condominium units is 63.

The building has a large, rectangular courtyard as its center core. On each floor, two corridors of condominium-unit entrance doors face onto each other across the courtyard. Each level of the street-facing, exterior walls of the building is finished entirely with windows from the floors-to-ceilings of the condominium units.

The standard units have studio-type living rooms with a ceiling height of 3.8m (12.5 ft). Staircases to loft-like parts of the living rooms maximize the usable space, so that the main area of the living room can accommodate a grand piano. The loft areas above the bathrooms, toilet closets and kitchens have ceiling heights of 1.4m (4.6 ft), and can be used as space for an extra futon or as storage. The areas around these utility-type rooms that have plumbing also used part of the available structural space for waterproofing appropriate to a multi-unit dwelling.

<< Sound Isolation Functionality and Sound Isolation Structural Design >>

For sound isolation between units above and below each other, we began with a layer of slabs 200 mm (7.8 in) thick. On top of this flooring base, we added a 120 mm (4.7 in) floating-floor material of moist-type glass wool.

In our estimation, the likelihood of sound leakage between units with contiguous walls was the more serious concern. Our strategy was four-layer walls having a concrete core 230 mm (9 in) thick, covered on both sides with 8 mm (.3 in)-thick sound-isolating walls made of mix of plaster and fibrous-material, plus a single layer of glass wool on one side of these three-layer walls.

For the windows, we used 12 mm (.5 in)-thick glass, and for the frames of the doors and window panes we used single-layer steel frames. The steel terrace doors are made to provide soundproofing functionality and slide open and closed on rollers using handles with built-in latches.

Because the unit ceilings are the slabs that form the first layer of the flooring of the level above, we anticipated that sound waves would travel through the slabs from one unit to the walls and frames of neighbors on the right and left. As a result, if sound transferred from one unit to a neighboring unit, the transferred sound would be even louder near the ceiling slab, the door and the window frames than it would be at the center of a unit's living room. Accordingly, to ensure that a sufficient level of isolation was achieved around the living room area where musical instruments are played, we set our sound isolation goal for the center of the units' living rooms at D-60 to 65.

<< Establishing "Music Time" Rules for the Condo's Residents >>

Since we expected that most residents would use the living room loft areas of their units as their sleeping areas, and because the ceiling slabs are likely to transfer sound from other units more strongly to the area at the top of the living room spaces where the lofts are located, we predicted that late night playing of musical instruments could have unpleasant consequences for neighbors who want a peaceful night's sleep. To prevent this problem, it was decided to include limitation clauses in the condo lease contracts both regarding the hours that instruments can be played and the maximum loudness of instruments permitted.

Musicians' Kawagoe's promotional brochure clearly states that the building imposes limitations on the kinds of instruments allowed (brass and percussion instruments are among the instruments specifically restricted) and that "lesson hours" are limited from 8:00 a.m. to 12:00 midnight. In determining the restrictions on musical instruments, we looked at the power-level data for each instrument and set an overall cut-off at 100 dB. Using this parameter, electrical instruments (such as those used in rock bands), most brass instruments, drums and timpani all have a power level above 100 dB and are therefore not allowed in Musicians' Kawagoe. Regarding the time limitations on playing musical instruments, while 12:00 midnight might seem too generous as an end time, the thinking of those who made the decision was that musicians would be understanding of other musicians in this regard.

<< Sound Isolation Performance Characteristics of This Project >>

Prior to the completion of the building, two units were readied for occupancy and opened for showing to the media and others. Before the model unit opened for viewing, we measured the sound isolation performance and confirmed that we achieved our goal for sound isolation capability (D-60 to 65).

During viewing hours of the model units, a grand piano was placed in one of the rooms and a college-age student from a local music conservatory was hired to play the piano continuously. Visitors to the model units had the opportunity to spend time in the unoccupied unit to hear for themselves the effectiveness of the structure's sound isolation. Our successful sound isolation strategy combined with the delicate playing style of the student pianist resulted in virtually total sound isolation between the two units. Over and over again, visitors to the unoccupied unit who had not seen the pianist themselves felt compelled to go and look inside the unit next door to assure themselves that someone was really playing the piano there.

Most of the visitors to the model unit were journalists from real estate magazines and related publications. They seemed glad to be able to experience first hand the effectiveness of Musicians' Kawagoe's sound isolation. According to one journalist, "There are some condominiums that claim to have a D-65 sound isolation performance level, but more sound can be heard between rooms than in this model unit, and there are properties owners who list sound isolation capabilities among their properties' specifications without ever measuring the units to confirm that the properties perform as claimed."

Measurement of the sound pressure level in Musicians' Kawagoe living rooms, at the center of the rooms, confirms that they achieve the D-60 to 65 sound isolation goal which we set as our objective. In addition, in the penthouse living rooms that have double the space of the standard living rooms, the sound isolation level achieved exceeds D-65.

<< Musicians' Kawagoe's Reputation among the Building's Residents >>

Musicians' Kawagoe caught the media's attention, with articles about it appearing in Japanese general circulation magazines such as Hanako, Brutus and Figaro Japon, and it has also been featured on TV. The entire building was leased within several weeks of being placed on the market, and there is apparently a long waiting list of people eager to occupy units in the building.

One month after all the units were leased and all the residents had moved in, the building's developer, Livlan Company, hosted a party for all of the residents in an open space area of the building known as the "Atelier." This space for community use is located on Musicians' Kawagoe's entrance level. The party gave residents an opportunity to socialize with each other, and it also gave both the developer and Nagata Acoustics the chance to ask residents their opinions of the building after one month of residence.

Among the residents of Musicians' Kawagoe are a husband and wife who are both professional vocalists, the harp player of one of Japan's top-rated orchestras, the horn player of a chamber orchestra and other accomplished musicians. The party included instrumental and voice performances by these residents. Contrary to our expectations, there were relatively few music conservatory or university students among the residents. Other than the professional musicians, most of the residents are people who play their musical instruments as a hobby.

All of the residents said that they are enjoying living at Musicians' Kawagoe. Even the professional musicians said that they did not feel hampered by the time restrictions on when they can play their musical instruments. Everyone was in agreement that they did not hear sound from other units.

The building developer, Livlan Company, has taken upon itself a larger role than the typical real estate management company. Using the Internet, Livlan plans to keep in contact with residents and to foster communication and the exchange of ideas and opinions among the residents of Musicians' Kawagoe. This extra step on the part of the developer will keep residents in touch with each other. It will also help forestall and prevent opinions about the rules of this specialized multi-unit dwelling from growing into acrimonious debates. The developer/landlord clearly has his clients' interests in mind and is satisfying their need for space to play musical instruments and have the benefit of quietness as well.

For more information about Musicians' Kawagoe, contact Livlan Company directly by phone at +81-48-474-2313, or by email at www.livlan.com (a primarily Japanese-language website).

Strategies to Solve the Growing Problem of Frequency Inverter Noise

by Hideo Nakamura

In recent years, the number of Japanese home appliances that have built-in frequency inverters has grown exponentially. Typical examples of these appliances include air conditioners, refrigerators and lighting fixtures.

The inverters, also known as frequency converters, adjust the frequency of electricity flowing to appliances and motors used for various purposes. In Japan, where utility companies provide most homes in the eastern part of the country with AC current at 50 Hz frequency, and homes in the western prefectures with AC current at 60 Hz, the use of inverters is linked to energy conservation and cost savings. Setting an appliance's inverter to adjust the incoming electrical power's frequency within a certain range based on specific conditions and algorithms, the appliance's energy use can be controlled precisely. When the inverter causes the appliance to use less energy, electrical bills decrease and energy is conserved. As the performance characteristics of inverters improve, their incorporation in home and industry appliances becomes more prevalent.

The use of inverters in industrial applications began before their widespread adoption in home appliances. Examples of apparatus that typically include inverters are electric trains and elevators.

<< The Noise Side Effect of Inverter Proliferation >>

Today, inverters provide valuable benefits and offer excellent performance and functionality. But there are also side effects. During the frequency conversion process, inverters either emit interference waves into the atmosphere or pass the waves to other equipment via electrical circuit connections, causing problems to another appliance or device.

Because of the way inverters work and the function they accomplish, their production and emission of interference waves is unavoidable. Therefore, the strategy to counteract inverter side effects must focus on protection from the inverter and the interference waves it emits. Luckily for homes and offices, these spaces usually do not have equipment that is sensitive to the interference waves produced by inverters. However, halls and theaters do have equipment that is sensitive to interference waves. In these kinds of spaces, the proliferation of inverter-generated interference requires appropriate strategies to address the problem.

<< Inverter Noise in Halls and Theaters >>

Halls and theaters use microphones and other equipment that rely on weak wave signals. As equipment such as elevators and HVAC systems increasingly contain embedded frequency inverters, this equipment becomes ever more likely to generate interference waves that pass through the hall's or theater's electrical circuitry into the microphones of the sound system, resulting in noise. The problem is not significant for the audiences of live performances, because the interference waves that pass into the microphone circuitry are at a very low level and would almost never be detected by listening audiences in normal live performance situations. However, noise from frequency inverters does become a problem when microphones are used to record a live performance in a hall or theater.

In particular, when a hall or theater is used by a broadcasting company or record label to record a live program or produce a music CD, the broadcaster or record company requires very low noise levels in the venue. When a hall or theater is used for these purposes, we hear of many cases of complaints about the presence of inverter noise. If a hall becomes stigmatized as inappropriate for broadcasts and recordings because of too high a noise level, its utilization rate can be adversely affected. The problem warrants serious attention for both aesthetic and economic reasons.

<< Inverter Noise is a Problem with a Clear Solution . . . >>

An answer to the question of how to accomplish inverter noise abatement already exists and implementing inverter noise abatement is not a difficult task, provided that it is done at the appropriate time. We know that inverter noise is almost always propagated through a device's electrical circuitry. Therefore, if we insert an interference-intercepting transformer into the inverter's electrical circuitry, the noise interference can be eliminated. (The transformer does not change the inverter's voltage.)

<< . . . But, a Solution Not Often Implemented >>

Given that we have a solution for the problem of inverter noise, it would seem to follow that when new halls and theaters are built, we could simply implement the solution of embedding an interference-intercepting transformer in devices that have inverters. Like an effective vaccine-this would make the problem disappear. In reality, this approach is not often followed, for the following reasons: (1) Electrical design subcontractors are not generally aware of the possibility of inverter noise. (2) Some halls and theaters with devices containing inverters have no inverter-noise problem, and current technology does not have a means for predicting the occurrence of inverter noise in advance of the problem being discovered during a hall's or theater's use. (3) The cost and space requirements of the interference-intercepting transformers needed for hall and theater HVAC systems that use large amounts of electrical power are substantial impediments, not so much because they are prohibitive in and of themselves, but because they represent an added expense to solve a problem that may never occur.

<< Difficulties in "Curing" Inverter Noise when Discovered in a Hall >>

It is unfortunate that inverter noise is rarely addressed using the preventive transformer strategy, because finding a "cure" after the noise occurs in a facility presents several difficulties. The location of the inverter causing the problem is neither predetermined nor predictable, and there can be no easy-to-follow or pre-established process for determining responsibility or the strategy for a remedy. As a result, the following problems arise.

First, there is the question of who should bear the cost of the remedy. Even if the inverter of a specific piece of equipment or device can be identified as the cause of the noise, if there is no reference in the hall's or theater's design documents regarding measures to be implemented to prevent inverter noise, the vendors and contractors who worked on the project will claim that they completed their work in accordance with the specifications provided and therefore have no responsibility for the noise.

In addition to the extra expense of solving an inverter noise problem after it is discovered, and the difficulty of deciding who pays for the fix, remedying the problem after a hall or theater is built also raises the difficulties of finding space for the transformer(s) as well as access through the building to carry the transformer(s) to the space selected. Sometimes, one or both of these two hurdles make remedying the inverter-noise problem physically impossible.

<< Who Pays the High Costs of Fixing Inverter-noise Problems ? >>

Depending on the specific situation of a hall or theater, and the cause of a detected inverter-noise problem, implementing a remedy can be more expensive than a prevention strategy would have cost during the appropriate phase of construction, especially when labor expenses are included. In the past, when halls and theaters first began to install equipment and devices with inverters, there was a lack of empirical experience and understanding of the possibility that an inverter noise problem could develop. Halls and theaters were unaware of the problem unless or until it occurred in their facility. Because the problem was still new and relatively rare and unknown, it was understandable that halls and theaters relied on remedies rather than prevention.

Today, however, despite the growing increase in the number of halls and theaters that have experienced the problem, halls and theaters continue to be planned and built without any budgetary provision for preventing or remedying inverter noise. When an inverter-noise problem is discovered, the remedial costs are foisted on the vendor or contractor that has the weakest position in defending itself against responsibility for the claim. As more halls and theaters ignore prevention, only to later discover an inverter-noise problem that necessitates expensive inverter-noise remedies, the practice of passing the bill for the fix to another party is unlikely to continue unchecked.

<< Compromise Remedies and Advance, Worst-case Planning >>

While the most complete and effective means to prevent or remedy inverter noise is to install an interference-intercepting transformer, it may be possible to provide a compromise remedy such as installing an electrical circuit shield or changing the setup of the circuit's ground, depending on how much of an impediment the noise interference is. Raising the possibility of compromise solutions runs the danger of complicating the issue. However, the proliferation of inverters in hall and theater equipment unequivocally necessitates that hall and theater designs make some provision for ensuring that inverter noise does not occur, or, at least, that fallback measures are included in design documents so that a clear remedial path exists should a remedy be required after construction is completed.

Advance consideration of a remedial strategy should include a description of the strategy to be followed if inverter noise occurs and who will bear responsibility for costs incurred in implementing the remedy. If this level of detailed information cannot be documented in the design stage, then at the very minimum, it should be provided to the general contractor before bidding begins on a project.

In Japan, this last alternative leaves much to be desired, especially if a project is funded from public coffers. Because there is no way to estimate in advance what the actual dollar value of a remedy may cost, should it be needed, there is also no way to reserve funds within a public project's budget as a kind of insurance against the possibility that inverter noise may occur. Therefore, for publicly funded halls, until the responsibility for remedial strategies can be fairly negotiated and defined, and unless preventive installation of interference-intercepting transformers becomes the norm, there will be no reliable business solution for handling the unfortunate discovery that a hall or theater has an inverter-noise problem.

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Nagata Acoustics News 00-10 (No.154)
Issued : October 25, 2000

Nagata Acoustics Inc.
Minami-Shinjuku-Hoshino Bldg. 8F, 5-23-13
Sendagaya, Shibuya-ku, Tokyo 151 Japan
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