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Creating active boundary conditions with Planar loudspeaker arrays to absorb and reflect sound
(2024) Müller, Anthea; Chalmers tekniska högskola / Institutionen för arkitektur och samhällsbyggnadsteknik (ACE); Chalmers tekniska högskola / Institutionen för arkitektur och samhällsbyggnadsteknik (ACE); Ahrens, Jens; Ahrens, Jens; Sarradj, Ennes
It was shown in the 1970s that a combination of two secondary sources are able to absorb sound
energy in one-dimensional sound propagation in a duct. The primary source can be interpreted
as being surrounded by a double-layer of secondary sources. This is inconvenient in two- and
three-dimensional scenarios as surfaces of secondary sources have to be used, which are difficult to
implement in practice. This thesis demonstrates that the same type of active absorption is possible
also in open space, i.e., when the secondary sources do not fully enclose the primary source.
In contrast to active noise canceling, the aim here is not to achieve active reduction in the downstream
area by increasing the sound level in the upstream area, but rather to actively remove
energy from the sound field. The focus here is particularly set on canceling out low frequencies to
facilite practical measurements. For this, two boundary conditions are set, one in the upstream
and one in the downstream area. To achieve the objective at the boundary conditions a set of FIR
filters must be determined. This is done here with the help of the LMS method, which is extended
to a MIMO (Multiple Input Multiple Output) system.
First the results of Swinbanks for the active reduction inside the one dimensional duct are recreated
with simulations and confirmed with an experiment. Based on these findings the approach is first
extended two dimensions to perform absorption of cylindrical waves with the help of two line
sources and then further extended to three dimensions to perform the absorption of spherical
waves by means of one-dimensional distributions of point sources. Two experiments are carried
out to confirm or refute the concepts introduced. These are first planned in detail with the help
of simulations. The first experiment (Setup 1) demonstrates the active absorption of cylindrical
waves emitted by line arrays in an outdoor free field setting. The second experiment (Setup 2)
demonstrates the active absorption of sound emitted by a point source that is actively absorbed
by curved arrays within a semi-anechoic chamber. The simulation results were confirmed in both
setups with the measurement results. They proof that the active control of the downstream area
whilst not influencing the upstream area is possible with the proposed boundary conditions within
the limitations of the method and their test environments. In both experiments active reduction
is achieved throughout the downstream area, achieving an averaged active reduction of 11 dB (3
dB over background noise level) in Setup 1 and an active averaged reduction of -27 dB (1 dB over
background noise level) in Setup 2 at the boundary condition. Throughout the upstream area the
average deviation from the undisturbed sound-field for Setup 1 is 0.3 dB, for Setup 2 it is 0.08 dB
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A Study in non-linear seat shaker processors for enhanced integration with full range audio systems
(2024) Ghijselinck, Lukas; Chalmers tekniska högskola / Institutionen för arkitektur och samhällsbyggnadsteknik (ACE); Chalmers tekniska högskola / Institutionen för arkitektur och samhällsbyggnadsteknik (ACE); Ahrens, Jens
This MSc Thesis studies the integration of non-linear seat shaker processors in a
full-range audio system, applied in the car environment. The thesis is conducted on
behalf of the Research and Development Department of Premium Sound Solutions.
The loudspeaker company wants to know more about the scientific implementation
and research behind seat shaker processors in cars. Studies have been done on the
subjective and objective influence of low-frequency sources, namely subwoofers, on
persons. Fewer studies have been done on the haptics and body reaction of lowfrequency
vibrational sound sources in a car environment.
The transmission of low frequencies in a car has a different modal directivity. The
signal affects both the auditory parts with the ear drums as the sensed parts in the
rest of the body. It is found that the auditory spectrum has an influence on the
perceived vibrations.
Therefore a first experiment is done to retrieve subjective data for the influence of
the low-frequency sound source on the body. The data is used to define the shaker
positioning with the corresponding threshold of feeling. Secondly, the vibration acceleration
levels are measured using accelerometers to retrieve the objective data.
Using that objective data, the excited acceleration levels are matched with those of
the subwoofer.
A second listening experiment is done in the form of an A/B listening test. The
interviewees are asked to quantify the difference of the perceived acceleration between
the subwoofer setup and the shaker implementation.
The subwoofer experiment showed that the threshold of sensing the vibrations in the
body is frequency-dependent. It is also found that vibrations are sensed in different
body parts. The excited body parts are also frequency dependent.
The results of the A/B experiment, where both sound pressure levels and acceleration
levels are matched, show that objective measurements and level matching have
the potential to be used as a tuning method. However the quality and implementation of
the used method can be improved
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(2024) Eklund, Nina; Chalmers tekniska högskola / Institutionen för arkitektur och samhällsbyggnadsteknik (ACE); Chalmers tekniska högskola / Institutionen för arkitektur och samhällsbyggnadsteknik (ACE); Ahrens, Jens
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Kvaliteter hos nyproducerade bostadsrätter som prioriteras av nutida köpare; analys av den nutida bostadsköparens behov
(2024) Ståhl, Edvin; Schillström, Tom; Chalmers tekniska högskola / Institutionen för arkitektur och samhällsbyggnadsteknik (ACE); Chalmers tekniska högskola / Institutionen för arkitektur och samhällsbyggnadsteknik (ACE); Ingelhammar, Caroline
Detta examensarbete har som syfte att undersöka eftertraktade kvaliteter vid köp av
nyproducerade bostadsrätter och hur de skiljer sig mellan generationer. Examensarbetet
ämnar att besvara frågeställningen: Vilka kvaliteter hos nyproducerade bostadsrätter är
prioriterade av nutida köpare? Analys av den nutida bostadsköparens behov.
Undersökningsmetoden som används är begränsade och består av kvantitativa enkäter för att
sedan fördjupas med hjälp av kvalitativa enkäter. Syftet med bakom upplägget är att få två
svar. Den kvantitativa enkäterna ska svara på vilka kategorier av preferenser som är centrala
och därefter kunna utforma de kvalitativa enkäterna för att specificera vad med dessa
preferenser som är av betydelse och hur de skiljer sig mellan våra målgrupper. Enkät är en
kostnad- och tidseffektiv metod för att samla in den data som ger svar på frågeställningen.
I samarbete med Ekeblad Bostad etablerades en målgrupp för undersökningen. Ekeblad
Bostad är ett medelstort bolag som startades 2010 med fokus på fastighetsutveckling och
nyproduktion. Bolaget har behov av att förbättra sin förståelse för vilka preferenser kunder
har för nyproducerade bostadsrätter som passar målgruppen. Ekeblad var därmed villiga att
bidra med sin kundkrets som population för att ta del av undersökningen.
Rapportens fokus är på nyproducerade bostadsrätter. Genom att observera kriterier såsom
läge, utformning, och marknadsförutsättningar fångas värdefulla insikter upp i de mest
frekvent flyttande åldersgruppers prioriteringar och förutsättningar för att komma in på
bostadsmarknaden.
Undersökningen behandlar inte priser på bostaden som en central faktor, utan väljer istället
att fokusera på tidigare nämnda fysiska kriterier. Den ekonomiska faktorn stör
undersökningens mål, vilket är att finna betydande skillnader utöver de som redan är
undersökt. En mindre sektion om ekonomi i våra enkäter inkluderas då undersökningen
därmed sätter prioriteringarna i relation till den ekonomiska faktorn då resultaten annars kan
bli förskjutna mot dyrare alternativ.
Målet med arbetet är att ta fram resultat som Ekeblads bostad ska kunna identifiera och
använda för att stärka sin verksamhet. Ekeblads Bostad skall förhoppningsvis kunna
identifiera relevanta resultat för deras verksamhet för att kunna fokusera på fortsatt analys av
den data som anses ha störst utvecklingspotential
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Integrating accessibility in the city planning process; investigating the case of Frölunda, Gothenburg using a systems approach
(2024) Jidah, Maria; El-Rifai, Rasha; Chalmers tekniska högskola / Institutionen för arkitektur och samhällsbyggnadsteknik (ACE); Chalmers tekniska högskola / Institutionen för arkitektur och samhällsbyggnadsteknik (ACE); Gil, Jorge
Gothenburg, like many urban centers, must improve its transportation infrastructure to tackle
environmental and social challenges. City planning plays a crucial role in addressing these
issues and promoting sustainable urban development. A central emphasis is on accessibility,
understood as the ease with which individuals can reach desired activities and destinations
using different transportation modes. City planning encompasses various elements such as
land-use and transport planning, which must be integrated to create accessible cities.
Accessibility is crucial in urban- and transport planning as it ensures equal opportunities,
promotes sustainability, and enhances the overall well-being of residents. This study
examines the integration of accessibility into city planning, focusing on Frölunda in
Gothenburg, Sweden. It comprises three main components: a theoretical framework derived
from a literature review, a case study of the Frölunda area examining how accessibility is
integrated in the city planning process, and an analysis of interviews. The main findings from
the literature review outlined several strategies for enhancing accessibility, including
stakeholder engagement, mixed land-use, and transit-oriented developments, while also
advocating for a systems approach that emphasizes feedback loops. Various planning
processes were identified: one based on the literature review, one from Gothenburg's policy
documents, and two based on the interviews, highlighting their misalignment. While the
literature emphasizes the complexity of the city planning process, highlighting the benefits of
utilizing a systems approach, Gothenburg policy documents depict a linear process.
Interviewees revealed that the linear process is not followed, where operational work often
precedes strategic planning. They envision the linear process to be implemented, while the
literature showcased that city planning is too complex to be perceived in that manner,
necessitating a systems approach. As a result, a targeted planning process was designed,
combining theoretical principles with empirical data. Key aspects were included, such as the
incorporation of feedback loops, coordination among stakeholders across planning phases,
and ensuring that the strategic-level output is finalized before initiating work at other levels