Tech Notes: Hydraulic Pile Drivers Work Out of a Tight Spot, Quietly

Driving piles is typically considered one of the noisiest, most disruptive activities at a construction job site.  The increased noise and vibration levels can disrupt ongoing client activity as well as adjacent neighbors.  However, new hydraulic pile-driving equipment may change this.

In a recent project to expand the paper making capacity of a Charleston, South Carolina paper plant a new foundation was required.  This project became complicated when is was learned that the old, vibration-sensitive paper machine needed to remain in place and in operation for as long as possible before the equipment switch.  Also, the initial work had to be completed in a space with only 12 feet of headroom.

Based on these requirements the contractor decided to use steel H-Piles and contacted Ken-Jet Industries Ltd. , of Missagua, Ontario, (416) 670-2436.  Ken-Jet Industries had just started distributing the Japanese-made Still Worker hydraulic piling machine in North America.  The Still Worker uses hydraulics to drive piles with a smooth, fluid motion that minimizes noise and vibration.  The unit operates at ground level.  It grips a pile and pushes it down about 3 feet then releases.  It then slides up 3 feet and grips the pile for another push.

Originally, the contractor for the project figured on driving one and a half 40-foot piles per shift.  After practicing with the Still Worker they were able to install 3-4 piles per shift.

Different versions of the Still Worker can be used to install and extract steel H-Piles and sheet piles.  The sheet piling equipment can “self travel” across the tops of installed piles.

The noise generated by the Still Worker is 20 decibels quieter than Vibro Hammers (1/4 as loud) and 30 decibels quieter than a Pile Hammer (1/3 as loud).  Vibration levels are 30 decibels lower than a Vibro Hammer (1/3 the vibration) and 50 decibels lower than Pile Hammers (1/10 the vibration).  This process should be considered for projects in acoustically critical environments.

(c) Thorburn Associates 1993

Driving piles is typically considered one of the noisiest, most disruptive activities at a construction job site.  The increased noise and vibration levels can disrupt ongoing client activity as well as adjacent neighbors.  However, new hydraulic pile-driving equipment may change this. In a recent project to expand the paper making capacity of a Charleston, South… Read more »

Tech Notes: Ceiling Mounted Microphones – A Solution or a Problem?

With hopes of eliminating tabletop or podium microphones, End Users, Designers and Architects frequently ask, “What about sticking them on the ceiling?”  Usually, what seems like an easy solution is not the best solution.

Ceiling mounted microphones are not recommended for the following reasons:

First, loudspeakers are typically mounted in the ceiling.  This places ceiling mounted microphones closer to the loudspeakers than to the person talking.  The nearness of the loudspeaker and microphone means that sound from the loudspeaker is likely to be louder than the speaker’s voice.  As shown in the diagram the primary sound picked up by the microphone is not the speaker’s voice, but the sound from the loudspeaker.  When this happens, the amplified signal is again picked up by the microphone, and that “high-pitched shriek” or feedback occurs.  In other words, there is no “volume gain before feedback.”

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Second, the most effective distance of the microphone from the sound source must be considered. For vocal microphones in a band this distance is a few inches, for microphones in a conference room setting the optimum distance is usually 1 to 3 feet. Ceiling mounted installations will exceed this optimum distance, which allows the microphone to transmit the speaker’s voice plus other unwanted sounds in the room (HVAC noise, fluorescent light buzz, etc.). The result is poor audio quality.

When can ceiling mounted microphones work?

They can be used to record speech or music for an archive record, not to reinforce speech or music.

They must be used in an extremely quiet room with a background noise criteria (NC) rating of no more than NC 20.

Michael Pettersen, Director of Consultant Liaison Program, Shure Brother’s Inc. contributed to this article

(C) Thorburn Associates 1993

With hopes of eliminating tabletop or podium microphones, End Users, Designers and Architects frequently ask, “What about sticking them on the ceiling?”  Usually, what seems like an easy solution is not the best solution. Ceiling mounted microphones are not recommended for the following reasons: First, loudspeakers are typically mounted in the ceiling.  This places ceiling… Read more »

Acoustical Terms – What Are They/What Do They Mean?

Recently we were asked “What is the difference between STC, NRC, and NC and are they interrelated?”

STC or Sound Transmission Class, describes how much sound a wall or a floor/ceiling construction will block from one room to the next. A good analogy to an STC rating is the fire rating of a partition. A two hour fire-rated assembly will keep the fire on the opposite side of the partition longer than a 20 minute assembly. Just like fire ratings, the higher the STC rating, the better the isolation. Therefore, an STC 50 partition will block more sound than an STC 30 partition.

NRC or Noise Reduction Coefficient, defines how much sound specific materials absorb. This is analogous to a room’s finishes. Just as various colors of paint, or textures, visually alter a room, various materials with different NRC ratings, such as carpet or tile, audibly alter a room. A material with a low NRC rating (tile) absorbs little sound and a material with a higher NRC rating (carpet) absorbs more sound.

Finally, NC or Noise Criteria measures how much mechanical noise can be heard in a room. This type of measurement can be compared to the amount of light in a room. A foot candle describes how much illumination a lighting fixture provides on a surface, NC describes how much mechanical system noise is heard in a room. The brighter the light on a surface the higher the foot candles, and the higher the NC rating, the more noise that is heard.

Are STC, NRC and NC related? Not really. They do interact in the total design of a room, just as the building structure, room finishes and lighting interacts on the visual design of a space. However, individually they all play separate roles. Room finishes are independent of the fire rating of the partition, just as the amount of sound a material absorbs is independent of its ability to block sound from one room to the next.

Hopefully these analogies of Sound Transmission Class to fire ratings; Noise Reduction Criteria to a room finish; and Noise Criteria to foot candles helps define and explain these acoustical terms.

© Thorburn Associates 1993

Recently we were asked “What is the difference between STC, NRC, and NC and are they interrelated?” STC or Sound Transmission Class, describes how much sound a wall or a floor/ceiling construction will block from one room to the next. A good analogy to an STC rating is the fire rating of a partition. A… Read more »

Office Acoustics

A question we are frequently asked by Project Managers is how can we improve the acoustical privacy between offices and work stations?

The level of acoustical privacy is defined as the amount of conversation that can be heard and understood between adjacent offices or work stations.

Before we can improve the acoustical privacy we must understand that there are three factors that control the acoustical environment:

– Noise Source
– Type of Partition Between Work Areas
– Level of Background Noise

To improve the acoustical environment in the work place we must determine how these factors relate to one another for each project.

The first factor is the noise source. How loud is the office machinery, the person talking on the telephone next door or the activity that occurs in the adjacent cubicle? This allows us to determine how much noise must be blocked from transmitting from one work station to another.

Next what is the type of partition/barrier/wall that exists between adjacent offices or work stations. Is it a full height wall or a 59” office partition? The partition type determines how much sound will be blocked.

Finally, what is the background noise level in the office. Background noise, as its name implies, is the quietest level of noise heard in an office on a continuous basis. These sounds may include heating or cooling systems, computer and printer fans, the buzz of fluorescent lights, and even traffic noise.

We have found Background Noise to be the most critical variable in this equation. Background noise varies within a building from cubicle to cubicle, office to office, and floor to floor. When you are near core mechanical shafts, where there often are support offices, the background noise heard is usually low frequency, rumbly, duct noise. When you are further away from the core along the duct run, where there are often perimeter offices, the background noise heard is usually the turbulence noise of air traveling through the diffuser.

The challenge is to identify an acceptable level of acoustical noise within the office layout and design.

The acoustical privacy between offices and work stations can be improved by various methods. Each method provides different levels of speech privacy, depending on your needs.

– Gypsum board Ceilings and/or Full Height Wall Partitions for Critical Spaces
– Partitions that Extend into the Plenum for Areas Requiring Confidential Speech Privacy
– Highly Absorptive Open Plan Office Partitions and Sound Masking for Normal Speech Privacy

The first diagram shows how the conversation in Room A can be heard above the background noise level in Room B. The characteristics of this partition type cannot reduce the conversation level below the level of background noise in Room B.

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In the second diagram, the acoustical privacy level has been improved. Now the characteristics of this partition type can reduce the conversation level below the background noise level. The conversation can no longer be heard in Room B.

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In future issues we will expand on Speech Privacy and Sound Masking.

(c) Thorburn Associates 1993

A question we are frequently asked by Project Managers is how can we improve the acoustical privacy between offices and work stations? The level of acoustical privacy is defined as the amount of conversation that can be heard and understood between adjacent offices or work stations. Before we can improve the acoustical privacy we must… Read more »

New Acoustical Product at AIA National Convention ’92!

While attending the recent AIA ’92 National Convention in Boston we took the opportunity to search the trade floor for new building materials with acoustical benefits.  The following summarizes our finds:

Among the more promising displays were acoustical wall and finish materials that would provide a durable interior finish while helping solve acoustical concerns.  Pyrok Inc. introduced a new acoustical wall and ceiling finish material that can be sprayed onto a ceiling, wall or open plenum.  This new product will allow interior designs developed around open ceiling grids, or exposed ducts and beams, to have a cost effective acoustical treatment.  The spray on material is relatively smooth when finished, has appearance of a concealed spine acoustical tile material, and can be installed for approximately the same price.  One advantage of the Pyrok material is that it is pigmented thus eliminating visible flaking.  A second advantage is the ability for freeform coverage of surfaces and constructions without the visible seams common of concealed spline materials.  There is also a fire proof version available at a higher price.

Laticrete International, a manufacturer of a thin and thick set tile mortar system, was showing their new product systems.  For a long time they have had a thin set mortar system that reduces fort-fall noise and other impact noise when compared to standard mortar systems.

Fabric & Architecture Magazine was giving away free issues.  This magazine is a good source for fabric finish ideas. This magazine is a good source for fabric finish ideas.  Fabric finishes, drapes, etc. are excellent acoustical finish materials.  Fabri finishes allow the interior designer to develop a finish system which they feel meets the aesthetic design requirements for the project.  At the same time, the light weight nature of the material allows the acoustical consultant to develop the acoustical room finish requirements in a cost effective manner with out infringing on the design requirements.

Porcelain Enamel Institute was displaying a product that would make a very durable wall finish material for “think tanks” and other rooms where the client wants “white boards” for walls.  The disadvantage of the material is that it is a very hard, acoustically reflective surface, and may cause problems if the other room finishes are not carefully selected.

The AIA ’93 Convention will be held in Chicago.  Hope to see you there!  If you would like to find out more about these products, please contact us.

(c) Thorburn Associates 1992

While attending the recent AIA ’92 National Convention in Boston we took the opportunity to search the trade floor for new building materials with acoustical benefits.  The following summarizes our finds: Among the more promising displays were acoustical wall and finish materials that would provide a durable interior finish while helping solve acoustical concerns.  Pyrok… Read more »

Acoustics and ADA

The Americans with Disabilities Act (ADA) has stirred up much controversy over the past year. This article will provide some practical guidelines for the public accommodations portion of these requirements. The new ADA hearing assistance requirements are not really new for Californians since the 1988 UBC, with the California Title 24 Amendment, has required hearing assistance systems.

The following summaries should help unravel the confusion surrounding these requirements.

Title 24 Section 611 (f) requires:

* Assembly areas with permanently installed public address systems provide assistive listening systems for people with hearing impairments.
* Exceptions: 1.This does not apply to systems used exclusively for paging, or background music, or a combination of these two uses. 2. Public and private schools are exempt from the requirements of this section.

The number of personal receivers required is based upon the capacity of the assembly area as follows:

Capacity # Receivers
1 to 99 0
100 to 200 8
201 to 300 12
301 to 400 16
401 to 500 20
over 500 20 + 1 for each additional 100 seats

ADA Section III-7.5180 Assembly Areas requires:

  • Fixed seating assembly areas that accommodate 50 or more people OR have audio-amplification systems must have a permanently installed assistive learning system.
  • Other assembly areas (not covered in above) must have a permanent system OR an adequate number of electrical outlets or other wiring to support a portable system.
  • A special sign indicating the availability of the system is required.
  • The minimum number of receivers must be equal to 4% of the total number of seats, but never less than two.

Because facilities will always be required to implement the “strictest” of the two codes we recommend the following as a guideline when designing audio-amplification requirements:

Capacity # Receivers
1 to 49 2
50 to 74 3
75 to 99 4
100 to 200 8
201 to 300 12
301 to 400 16
401 to 500 20
over 500 20 + 1 for each additional 100 seats

The bottom line, as put by the America Speech-Language-Hearings Association’s response to the ADA was:

“Ask people about their needs, show respect and sensitivity, use what works (not necessarily what is most expensive), and use your resources creatively and effectively.”

From a design perspective, any time an audio system that is used for speech reinforcement or audio playback is part of your contract documents, an assistive listening system should be part of the design.

(c) Thorburn Associates 1992

The Americans with Disabilities Act (ADA) has stirred up much controversy over the past year. This article will provide some practical guidelines for the public accommodations portion of these requirements. The new ADA hearing assistance requirements are not really new for Californians since the 1988 UBC, with the California Title 24 Amendment, has required hearing… Read more »