Reflected Wave Reduction Based on Time-Delay Separation for the Plane Array of Multilayer Acoustic Absorbers

This paper presents a control technique for reducing the reflection of acoustic signals for the plane array of multilayer acoustic absorbers underwater. In order to achieve this, a plane array of multilayer acoustic absorbers is proposed to attenuate low-frequency noise, with each unit consisting of a piezoelectric transducer, two layers of polyvinylidene fluorides and three layers of the acoustic window. Time-delay separation is used to find the incident and reflected acoustic signals to achieve reflected sound reduction. Experimental comparison of the attenuation rate of the reflected acoustic signal when performing passive and active controls is considered to verify the effectiveness of the time-delay separation technique applied plane array absorbers. Experiments on the plane array of smart skin absorbers confirmed that the reduction of reflected acoustic signals makes it suitable for a wide range of underwater applications.

Effects of Wall-to-Wall Supported Ceilings on Impact Sound Insulation for Use in Residential Buildings

In Korean residential buildings, floor impact sounds were reduced over the past few decades mainly through a floating floor system. However, ceiling constructions for impact sound reduction have not been applied actively because of a lack of useful information. This study focuses on the effects of wall-to-wall supported ceilings (WSC), which are designed with construction discontinuities between concrete slabs and ceilings, and the damping caused by porous absorbers for impact sound insulation. To examine the impact sound insulation according to ceiling conditions, measurements were performed in 25 floor–ceiling assemblies. The results indicate that ceiling treatment is mostly useful in reducing the floor impact sound. The floor impact sound owing to the WSC decreased by 2–7 dB and 2–8 dB in terms of the single number quantity for the tapping machine and rubber balls, respectively, compared with representative existing housing constructions wherein ceilings were attached on wooden sticks. Furthermore, the reduction effect of the WSC appeared to be more profound when it was applied to the floor–ceiling assembly with poor impact sound insulation. Thus, the WSC can be used to enhance the impact of sound insulation of existing housings without major repairs of floor structural layers.

Sound Reduction of Ventilation Ducts through Walls: Experimental Results and Updated Models

Ventilation ducts can have a negative effect on the sound reduction index between two rooms if they pass through the dividing structure without treatments. The overall sound reduction of a ventilation duct is dependent on several factors including the transmission loss when sound is breaking in and out from the duct. This study aims to model the sound reduction of a combined system with a separating wall and a ventilation duct through it. Three walls, characterized according to ISO 717-1, are combined with three different ventilation ducts, two circular and one rectangular with different dimensions. Laboratory measurement data are used to determine the sound reduction of the different configurations and the type of treatments needed for each configuration. A proposed model with existing theory for describing sound transmission losses of circular and rectangular ventilation ducts predicts the shape of the measurement data for many frequency bands. A new theory part is developed through an iterative process for circular ducts, which is based on measurements with previous methods and studies as a guide because the existing prediction scheme is somewhat perplexing. For rectangular ducts, the existing theory has been updated to better match measurement data. The application of the proposed theory and model in this article shows similar results when compared to measurements. The difference in weighted sound reduction index between developed theories and measurement data is 0–1 dB for every configuration.

Perforated Steel Stud to Improve the Acoustic Insulation of Drywall Partitions

Steel studs are an inevitable part of drywall construction as they are lightweight and offer the required structural stability. However, the studs act as sound bridges between the plasterboards, reducing the overall sound insulation of the wall. Overcoming this often calls for wider cavity walls and complex stud decoupling fixtures that increase the installation cost while reducing the floor area. As an alternative approach, this research reveals the potential of perforated studs to improve the acoustic insulation of drywall partitions. The acoustic and structural performance is characterized using a validated finite element model that acted as a prediction tool in reducing the number of physical tests required. The results established that an acoustic numerical model featuring fluid-structure-interaction can predict the weighted sound reduction index of a stud wall assembly at an accuracy of ±1 dB. The model was used to analyze six perforated stud designs and found them to outperform the sound insulation of non-perforated drywall partitions by reducing the sound bridging. Overall, the best performing perforated stud design was found to offer improvements in acoustic insulation of up to 4 dB, while being structurally compliant.

Mechanism of reduction of aeroacoustic sound by porous material: comparative study of microscopic and macroscopic models

The effects of porous material on the aeroacoustic sound generated in a two-dimensional low-Reynolds-number flow ( $Re=150$ ) past a circular cylinder are studied by direct numerical simulation in which the acoustic waves of small amplitudes are obtained directly as a solution to the compressible Navier–Stokes equations. Two models are introduced for the porous material: the microscopic model, in which the porous material is a collection of small cylinders, and the macroscopic model, in which the porous material is continuum characterized by permeability. The corrected volume penalization method is used to deal with the core cylinder, the small cylinders and the porous material. In the microscopic model, significant reduction of the aeroacoustic sound is found depending on the parameters; the maximum reduction of $24.4$ dB from the case of a bare cylinder is obtained. The results obtained for the modified macroscopic model are in good agreement with those obtained for the microscopic model converted by the theory of homogenization, which establishes that the microscopic and macroscopic models are consistent and valid. The detailed mechanism of sound reduction is elucidated. The presence of a fluid region between the porous material and the core cylinder is important for sound reduction. When the sound is strongly reduced, the pressure field behind the cylinder becomes nearly uniform with a high value to stabilize the shear layer in the wake; as a result, the vortex shedding behind the cylinder is delayed to the far wake to suppress the unsteady vortex motion near the cylinder, which is responsible for the aeroacoustic sound.

LITERATUR REVIEW: TERAPI NON FARMAKOLOGIS UNTUK MENINGKATKAN KUALITAS TIDUR PASIEN DI ICU ATAU CCU

Sleep is one of the basic human needs. Good quality sleep can increase the improvement of the disease. Sleep disturbances are common among hospitalized patients in CCU and ICU. The purpose of this literature review is to compare several research results on non-pharmacological therapies (eye masks, earplugs, music therapy, turning off lights, environmental modifications) in improving sleep quality to determine the best nursing action and safe for treating sleep disorders patients. Search articles using the PICO framework in the database; Google Scholar, Ebscho, Science direct, Elseiver, MedLine, CINAHL, PubMed, and ProQuest, limited to the last 10 years; 2011 to 2021, 10 International Journals were obtained. Improved sleep quality can be done in several ways; the use of eye masks, earplugs, music therapy, light and sound reduction, switching treatment schedules outside of bedtime, and combinations. The results of the review show schedules outside of bedtime, and combinations. The results of the review show that the most effective actions applied locally to improve sleep quality are reducing lighting and noise and diverting treatment schedules outside of bedtime because it is easy, safe, and does not cost money. If the intervention has not helped, eye masks, earplugs, and/or music can be offered according to the patient's choice, local culture, and facilities available at the hospital. Further research is needed on patients outside the ICU/CCU with a larger number of samples, different age and condition characteristics, longer treatment duration, and using objective sleep quality measurement tools such as polysomnography.

Perforated Steel Stud to Improve the Acoustic Insulation of Drywall Partitions

Steels studs are an inevitable part of drywall construction as they are lightweight and offer the required structural stability. However, the studs act as sound bridges between the plasterboards reducing the overall sound insulation of the wall. Overcoming this often calls for wider cavity walls and complex stud decoupling fixtures that increase the installation cost while reducing the floor area. As an alternative approach, this research reveals the potential of perforated studs to improve the acoustic insulation of drywall partitions. The acoustic and structural performance is characterized using a validated finite element model that acted as a prediction tool in reducing the number of physical tests required. The results established that an acoustic numerical model featuring fluid-structure-interaction can predict the weighted sound reduction index of a stud wall assembly at an accuracy of ±1 dB. The model was used to analyze six perforated stud designs and found to outperform the sound insulation of non-perforated drywall partitions by reducing the sound bridging. Overall, the best performing perforated stud design was found to offer improvements in acoustic insulation of up to 4 dB, while being structurally compliant.

Additional noise reduction with diffracting elements on barriers: experimental testing

The noise reduction of a (low) noise barrier can be enhanced by using an additional element with quarter-wavelength resonators with varying depths. The so-called WHISwall or WHIStop deflects sound upwards for specific frequencies creating an additional sound reduction. Different experiments on the WHISwall and WHIStop are performed as input for model validation. The development and validation of the model are described in a separate paper. In this paper the measurement campaign and its results are presented. We performed measurements on two setups. The first setup consists of a 1.1 meter high WHISwall, a 1.1m high noise barrier and a reference section (without noise measure). Measurements have been conducted with both an artificial sound source and pass by measurements with light and heavy motor vehicles. In a second test setup, the WHIStop was placed on top of a 4 meter high noise barrier and the diffraction was determined according the European standard EN 1793-4.

Sound absorption based on Micro-perforated panels and Acoustic Black Hole principle

Acoustic black holes (ABHs) have been so far investigated mainly for bending wave ma-nipulation in mechanical structures such as beams or plates. The investigations on ABHs for sound wave manipulation, referred to as Sonic black holes (SBHs) are scarce. Existing SBH structure for sound reduction in air is typically formed by putting a set of rings inside a duct wall with decreasing inner radius according to a power law. As such, the structure is very complex and difficult to be practically realized, which hampers the practical application of SBHs for sound reduction. This study explores the possibilities of achieving SBH effects using other types of structural configurations. In particular, micro-perforated panels are proposed to be introduced into the conventional SBH structure, and the simulation results show that the new formed SBH structure is simpler in configuration in terms of number of rings and more efficient in terms of sound energy trapping and dissipation.