Sound Transmission Class Ratings Research Articles

Development and analysis of Fe-doped ZnO nanoparticle-infused sisal fiber reinforced hybrid polymer composites for high-performance sound absorption and thermal insulation applications

In the current study, sisal fiber-reinforced hybrid composites have been developed by integrating a bidirectional mat with a blend of epoxy using Fe-doped ZnO (IDZO) nanoparticles at concentrations of 0.2, 0.4, 0.6, and 0.8 wt%. Hand-lay-up approach was used to create the composites. The composites were characterized through a comprehensive analysis of their density, water absorption, elasticity, thermogravimetric analysis, mechanical resistance, thermal conductivity, microhardness, and propagation of sound properties, including sound absorption coefficients and sound transmission class ratings. As filler loading increased, the bio-composite sample’s hardness increased under the density and void volume fraction values, with 0.8 wt% composite sample showing the superior micro-hardness. A positive correlation was observed between the ZnO nanoparticle weight percentage and thermal conductivity, with improve nanoparticle content leading to improved thermal performance. Composites containing 0.4 wt percent nanoparticles showed superior tensile strength (66.8–84.16 MPa), flexural strength (97.69–120.02 MPa) and flexural modulus (3.56–7.68 GPa). It has been observed that the weight percentage of IDZO filler greatly influences the sound absorption efficiency of the current composites. These findings highlight the promising potential of these novel biocomposites in advanced engineering applications, emphasizing their usefulness in demanding environments with biodegradability and high-performance thermal, mechanical, and acoustic properties. Based on the sound transmission class ratings, the sisal fiber biocomposites have been regarded as great adoptions for use as sound-absorbing materials such as wall partitions, doors, enclosures, and structural components, thermal insulation systems, and electrical insulation.

An investigation of the sound transmission class rating system using large-volume, high-variability datasets

From shortly before, ASTM International introduced the E90-61T classification method in 1961 to the present time, the use of the sound transmission class (STC) rating system in North America expanded arguably more than any other building acoustics metric available today. From building codes to architectural specifications, the STC rating continues to connect acoustical engineers to building designers and occupants as a method for conceptualizing sound isolation in buildings, notwithstanding a valid evidence basis for significant flaws in the STC calculation methodology. Modern innovation in acoustic treatment introduces a far greater variety in achievable sound isolation performance than when the STC was first introduced. PABCO Gypsum has performed thousands of standardized sound transmission loss (STL) testing, providing a large and varied sample from which to observe trends. This paper utilizes this large-volume sample to compare tested assemblies with the same or similar STC ratings. STL data will be observed and compared to probable loudness level differences with the hope that this information will motivate further research and change in sound isolation classification methodology.

Investigation of alternative methods for measuring and evaluating airborne sound insulation

The reproducibility of airborne noise insulation testing is poor, as documented by various interlaboratory studies. This is compounded by the definition of Sound Transmission Class (STC), the dominant single-number rating used in North America, which over-emphasizes the wall performance at and around the 125 Hz third-octave band. Small variations in performance at these frequencies can result in substantial changes in STC rating. To address these concerns, changes to both the measurement method and the single number ratings may be appropriate. For the former, the authors have begun an investigation of measuring the vibro-acoustic characteristics of walls, including measuring the vibration on the surfaces of the separating assembly and the flanking assemblies. This may result in increased precision of sound insulation measurements. For the latter issue, the authors have performed statistical evaluation of published wall sound insulation tests to clarify the effects of idiosyncrasies in the definition of STC and investigated whether different rating methods may better describe the performance of wall assemblies.

A case study in the measurement of door sound isolation with ASTM test standards

The use of the door transmission class rating in lieu of the apparent sound transmission class rating has yet to gain traction within building codes and specified project requirements. This paper presents a case study involving performance requirement testing conducted at a university's media facility, in which sound insulation properties were a critical design and construction focus. Both test methods described in ASTM E2964 and ASTM E336 were performed where a door was the test partition. Door transmission class ratings were presented in comparison to apparent sound transmission class ratings for the same partition. Testing was performed in a variety of situations, including scenarios both inside and outside of the minimum requirements of testing standards. Our analysis considers the effectiveness of the recently adopted ASTM E2964 in comparison to the methods of the ASTM E336. We also consider some of the subtle differences between the two test methods and how they may impact the testing of certain adjacencies.

Achieving minimum impact insulation class 50 rating using resilient clip technology in lightweight construction.

Resilient clip technology is an alternative to resilient channel for supporting gypsum wallboard in fire rated wall and floor-ceiling assemblies. Lightweight wood frame construction presents challenges in meeting building code requirements for impact insulation class (IIC) and sound transmission class (STC) ratings in floor-ceiling assemblies. Through laboratory testing we were able to compare different floor-ceiling assemblies commonly used in multi-family construction. Two different structures were tested, an 18 in. open web truss, 24 in. o.c., and a 12 in. engineered joist (TJI) 24 in. o.c. Various finish floor coverings were used including ceramic tile, vinyl, and engineered wood. Structures achieved minimum IIC and STC 50 with and without 3/4 in. Gypsum concrete. Resilient rubber underlayment of varying thickness can further improve the IIC and STC ratings of the assembly as can adding a second layer of gypsum wallboard.

Novel method of measuring sound from footfall to understand impacts in space below

Sound generated by people walking overhead made a conference room and law library unusable in the offices of a lawyer. Employing sound transmission class (STC) and impact insulation class (IIC) test procedures to quantify sound impacts in the space proved useless in understanding the complaints caused by the footfall. That is, the STC ratings and IIC ratings were sufficiently high that complaints would not have been expected. The floor/ceiling assembly was light weight with 28 ft long girders and open web trusses 35 ft long and 24 in. on center. The floor was constructed with two layers of plywood on top, and the trusses and the ceilings were either gypsum board or suspended acoustical tiles. Floors were finished with commercial carpet, vinyl composition tile, and carpet and padding. Short duration sound measurements in the frequency range 12.5 Hz to 10,000 Hz were made to quantify the difference in background sound and footfall generated sound. The very large differences in sound pressure levels at individual one-third-octave band frequencies and the A-weighted sound level clearly shows why complaints would be expected. The influence of floor and ceiling finish is seen in these measurements. The results provide clues to solutions to the problem with the assembly.

A method to prove violation of building code sound insulation standards in small condominiums

Building code sound insulation standards are health measures intended to protect people from excessive noise. In the USA, minimum values for Field Sound Transmission Loss (FSTC), and Field Impact Insulation Class (FIIC) are widely used to rate noise insulation between adjacent condominiums. Current American Society for Testing and Materials (ASTM) field test standards specify minimum room volumes for each of 16 one-third octave band test frequencies. For field impact insulation class ratings (FIIC), ASTM E 1007 specifies a minimum room volume of 2100 ft3 for valid measurement in the 100-Hz band. For air-borne sound transmission class ratings (FSTC), ASTM E 336 specifies minimum room volumes of 1400 ft3 for valid measurement in the 125-Hz band. FIIC and FSTC cannot be determined for bedrooms and kitchens of smaller condominiums which fail the minimum size requirement for the lowest bands. However, upper bounds can be determined merely by excluding invalid lower bands from computations. It is shown that when the upper bound on FIIC or FSTC falls below the code requirement (field values of 45 under the Uniform Building Code and the International Building Code), one may logically conclude that the code requirement is violated under existing standards.

Fire-resistance and Sound-transmission-class Ratings for Wood-frame Walls

A collaborative industry-government research program was carried out at the National Research Council Canada (NRC) to develop new sound-transmission-class and fire-resistance ratings for gypsum-board protected walls. Forintek Canada Corp. and the Canadian Wood Council participated in the program on behalf of Canada's wood industry. As a result of that NRC research program, sound-transmission-class (STC) and fire-resistance (FR) ratings were formulated for approximately 140 gypsum-protected wood-frame walls. Fire-resistance ratings for the walls range from 30 minutes to 2 hours. Sound-transmission-class ratings range from 30 to 65. Sound-transmission-class and fire-resistance ratings for approximately 90 of the wall designs appear in tbe 1995 edition of the National Building Code of Canada (NBCC). This paper highlights some of those STC and FR ratings and describes how they were derived from the data obtained through the research program.

Sound transmission through very porous concrete blocks

Sound transmission loss measurements through a wall constructed from very porous concrete blocks gave some interesting results. The unfinished block wall had a sound transmission class (STC) rating of 14. This was increased to only 29 by screwing a layer of drywall to one side of the block wall. The drywall, while it provides a sealed surface, is not well enough bonded to the blocks and can still vibrate fairly freely. Plastering increased the STC to 43. The porosity of the block increased the effective depth of the air space behind the drywall. This lowered the mass‐air‐mass resonance substantially and, with drywall supported on steel studs, plastered block wall systems gave very good STC ratings. Walls constructed using this type of block can give STC ratings about as high as those obtained with heavier normal weight blocks. Measurements were made down to 63 Hz and revealed that in many cases there are resonances occurring below 125 Hz that have a strong influence on transmission loss values at and above 125 Hz. Measurement to these low frequencies give a clearer picture of the effect of changes to the wall structure. The results obtained will be presented and discussed.

Exterior sound transmission through fenestration products—Do we need a new rating method

The California Association of Window Manufacturers (CAWM) requested ASTM to develop test criteria and performance ratings for exterior sound control capabilities of fenestration products. This presentation considers the relationship between sound transmission class (STC) and traffic, aircraft, and rail noise reduction (NR) for a group of glass configurations tested by Monsanto. It will be shown that a clear relationship exists between glass STC and noise reduction, which depends upon source spectrum shape and glazing configuration. It will be shown that any new rating method would necessarily take the form of the glazing STC rating plus a constant related to source spectrum type. Other features of building exterior construction will be considered, as they affect the minimum acceptable NR required for fenestration in any particular application. This obviates any benefit that a new rating scheme, dealing more directly with fenestration products, might have over the current STC rating method. A simplified method for estimating minimum required STC will be presented which will provide the advantage that the CAWM now seeks through a new fenestration products sound transmission loss rating. [Work partly supported by Monsanto.]

Study of the sound transmission class system for rating building partitions—Another view

In an earlier paper, Clark [J. Acoust. Soc. Am. 47, 676–682 (1970)] concluded that the ASTM classification method E413 for determining a single-number rating for sound transmission loss characteristics yields conservative values when there are large dips in the TL curve of the partition. That is, Clark found that the sound transmission class (STC) rating method was more sensitive to dips in sound transmission loss than his subjective experimental responses would indicate. Clark also concluded that the rule which limits the deficiency in TL in any 1/3-octave band to 8 dB is unnecessary. Clark’s experimental method consisted of matching the annoyance produced by sounds filtered in accordance with the ASTM reference transmission loss (TL) contour shape with the annoyance produced by sounds filtered by a similar contour with octave-band or 1/3-octave-band dips of various depths. This was done by adjusting the sound transmitted by the reference STC contoured channel to have the same perceived annoyance as that produced by the sound transmitted by the channel containing the TL characteristic with dip. If instead, the sound transmitted by the STC filtered channel had been held constant at the chosen reference level of annoyance, and the channel simulating the TL characteristic with the dip had been adjusted to match the reference annoyance, quite different results would have been obtained. In this paper, the articulation index has been used to predict the results of Clark’s experiment for speech signals. When the TL filtered channel with notch was adjusted to produce the same articulation index of approximately 5%, the results show that the STC rating procedure is not conservative. Rather it overrates TL characteristics with high-frequency octave-band dips by as much as 5 dB. Instead of abandoning the 8-dB rule completely, it is proposed that it be replaced by a limitation of 16 dB for the sum of the deficiencies in any three adjacent 1/3-octave bands.

Subjective study of the sound-transmission class system for rating building partitions.

The use of single number ratings in describing the acoustic performance of various building elements is very common. Examples of this are the sound-transmission class (STC) of a wall or the impact-noise rating of a floor. In the STC rating method, a transmission-loss (TL) curve of irregular shape is compared to a standard-reference curve. The contribution of various frequency bands depends on the shape of the standard curve and the method of comparison. An experiment has been carried out to determine the relative subjective importance of the various frequency bands and how the change in subjective rating due to irregularities in a TL curve compares with the rating obtained by using the standard curve and fitting rules. Results indicate that the present STC rating system is overconservative in rating changes in a TL curve and that narrow coincidence-type dips are not very important.

Effect of Shape of Transmission-Loss Curve on Subjective Reaction to Transmitted Noise

The use of single-number ratings is quite common in describing the acoustic performance of various building elements, e.g., the sound-transmission class of a wall or the impact-noise rating of a floor. The determination of single-number ratings involves certain assumptions regarding the relative importance of various frequency bands. In the sound transmission class (STC) rating system, for instance, a TL curve of irregular shape must be compared to a standard reference curve. The contribution of various frequency bands depends on the shape of the reference curve and on the method of comparison. An experiment has been carried out to determine subjectively the effect of various irregularities in TL curves as compared to a standard curve such as the STC contour. Results so far show that for frequencies in the range 500, 1000, and 2000 Hz, a dip 1 oct wide would effectively reduce the STC rating by 5 as compared to a dip 13 oct wide of the same depth.