Aaltodoc Repository :: Browsing by Author "Lokki, Tapio"

Browsing by Author "Lokki, Tapio"

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Aalto University - Acoustics Lab: Lab presentation
(2021) Lokki, Tapio; Meyer-Kahlen, Nils; Schlecht, Sebastian; Välimäki, Vesa; Dept Signal Process and Acoust; Department of Art and Media; Department of Media; Virtual Acoustics; Lokki Tapio group; Audio Signal Processing
The professor’s and researchers working at the Aalto Acoustics Lab have prepared video presentations and demos in the special facilities of the laboratory. The laboratories were renovated two years ago, so they are now in great shape. Most of the video material is recorded binaurally so that it can be enjoyed well with headphones.
Äänen hyödyntäminen käyttöliittymissä
(2012-04-29) Hilvenius, Jarno; Lokki, Tapio; Tietotekniikan laitos; Perustieteiden korkeakoulu; Janhunen, Tomi
Äänen vaimentuminen huokoisissa materiaaleissa
(2020-12-11) Köhler, Peter; Lokki, Tapio; Sähkötekniikan korkeakoulu; Turunen, Markus
Äänentoistolaitteiston äänenlaadun mittaaminen
(2013-05-30) Lehtonen, Lauri; Lokki, Tapio; Perustieteiden korkeakoulu; Immonen, Stina
Äänikäyttöliittymät
(2012-04-28) Nevalainen, Jere; Lokki, Tapio; Tietotekniikan laitos; Perustieteiden korkeakoulu; Tomi Janhunen
Ääntä absorboivien materiaalien sijoittelun vaikutukset huoneakustiikkaan
(2022-05-13) Pahta, Arttu; Lokki, Tapio; Sähkötekniikan korkeakoulu; Aalto, Samuli
Absorption of gilding in concert halls
(2020-12) Lokki, Tapio; Pätynen, Jukka; Dept Signal Process and Acoust; Lokki Tapio group; Virtual Acoustics; Akukon Ltd
A few renowned concert halls have walls, statues, and ceiling surfaces covered at least partially with gilding. Despite its appearance, such material is not actually gold. Instead, it is composition gold, which is a very thin leaf of copper-tin-zinc alloy, finished with shellac lacquering. In order to investigate the effect of treatments on room acoustics, we asked an artisan, a Master Gilder, to prepare gypsum cylinders that were pre-cut to diameter of 29 mm for impedance tube measurement. The top surfaces of these specimens were treated either with composition gold, real 24 carat gold leafs without shellac, or linseed oil paint. The absorption coefficients of all these cylinders were measured with an impedance tube. Each specimen was measured on both sides to provide a direct comparison between different surface treatments to untreated gypsum. This paper describes the measurement process, the practical issues encountered in fitting the specimens tightly for measuring, and finally the results of the measurements. The results show that the absorption coefficient of the composition gold is 0.02 over a wide frequency range, and it absorbs approximately 50% less sound energy than bare gypsum.
Acoustic Coatings—A Discreet Way to Control Acoustic Environment
(FRONTIERS MEDIA SA, 2021-05-11) Cucharero, Jose; Hänninen, Tuomas; Makkonen, Marko; Lokki, Tapio; Department of Information and Communications Engineering; Dept Signal Process and Acoust; Department of Computer Science; Virtual Acoustics; Lokki Tapio group; Lumir Oy
Acoustic comfort is directly related to enhanced well-being and performance of people. A typical challenge faced by architects and acousticians is to achieve adequate acoustics while maintaining the aesthetics of the space and reducing the visual aspects of acoustic materials and elements. In this study, we present a biofiber-based acoustic coating as a feasible solution to improve acoustic environments while preserving the aesthetics of spaces. An acoustic coating is a thin layer of absorption material, but the coating can be sprayed on other sound absorbing structures to make it more effective on a wide frequency range. In addition, this biofiber-based coating acts as a carbon sink during its operating life, thus reducing the carbon footprint of the building. Therefore, the coating is sustainable and is an environmental friendly solution. The absorption properties of the biofiber-based coating are demonstrated in the present study with three case studies, which all had demanding requirements to conceal the acoustic structures.
Acoustic Multi-Microphone Beamforming in a Practical Form Factor
(2017-04-03) Kiiski, Roope; Mäkinen, Kalle; Saksela, Kai; Sähkötekniikan korkeakoulu; Lokki, Tapio
Signal quality and noiselessness is important for Automatic Speech Recognition and communications. These can be achieved with the help of microphone arrays and beamforming. Multiple microphones can be used to pick sound coming from one direction while attenuating other directions. In this thesis, three arrays and three beamformers are compared. The target is to see how different structures affect the output signal and if one of the arrays is superior to the others. The results show that the baffled array appears bigger than the reference array or the array on the top surface of a cylinder, but it adds complexity to the beamformers. For Automatic Speech Recognition, all three arrays performed the same, but there were clear differences between the beamforming algorithms. Thus the array to use depends on the use-case and especially on the industrial design of the device.
An acoustic paintbrush method for simulated spatial room impulse responses
(2020-09) Puomio, Otto; Pihlajakuja, Tapani; Lokki, Tapio; Dept Signal Process and Acoust; Virtual Acoustics; Lokki Tapio group
Virtual reality applications require all kinds of methods to create plausible virtual acoustics environments to enhance the user experi- ence. Here, we present an acoustic paintbrush method that modifies the timbre of a simple room acoustics simulation with the timbre of a measured room response while aiming to preserve the spatial aspects of the simulated room. In other words, the method only applies the measured spectral coloration and alters the simulated and temporal distribution of early reflections as little as possible. Three variations of the acoustic paintbrush method are validated with a listening test. The results indicate that the method works reasonably well. The paintbrushed room acoustic simulations were perceived to become closer to the measured room acoustics than the source simulation. However, the limits of the perceived effect varied depending on the input signal and the simulated and recorded responses. This warrants for further perceptual testing.
Acoustic Properties of Aerogels: Current Status and Prospects
(WILEY-VCH VERLAG, 2023-03) Budtova, Tatiana; Lokki, Tapio; Malakooti, Sadeq; Rege, Ameya; Lu, Hongbing; Milow, Barbara; Vapaavuori, Jaana; Vivod, Stephanie; Department of Information and Communications Engineering; Department of Chemistry and Materials Science; Virtual Acoustics; Lokki Tapio group; Multifunctional Materials Design; NASA Glenn Research Center; German Aerospace Center; University of Texas at Dallas; École des mines Paris
Noise reduction remains an important priority in the modern society, in particular, for urban areas and highly populated cities. Insulation of buildings and transport systems such as cars, trains, and airplanes has accelerated the need to develop advanced materials. Various porous materials, such as commercially available foams and granular and fibrous materials, are commonly used for sound mitigating applications. In this review, a special class of advanced porous materials, aerogels, is examined, and an overview of the current experimental and theoretical status of their acoustic properties is provided. Aerogels can be composed of inorganic matter, synthetic or natural polymers, as well as organic/inorganic composites and hybrids. Aerogels are highly porous nanostructured materials with a large number of meso- and small macropores; the mechanisms of sound absorption partly differ from those of traditional porous absorbers possessing large macropores. The understanding of the acoustic properties of aerogels is far from being complete, and experimental results remain scattered. It is demonstrated that the structure of the aerogel provides a complex three-dimensional architecture ideally suited for promising high-performance materials for acoustic mitigation systems. This is in addition to the numerous other desirable properties that include low density, low thermal conductivity, and low refractive index.
Acoustic visualizations using surface mapping
(2014) Siltanen, Samuel; Robinson, Philip; Saarelma, Jukka; Pätynen, Jukka; Tervo, Sakari; Savioja, Lauri; Lokki, Tapio
Acoustics in communal libraries: common problems and their solutions
(2016-10-27) Santaholma, Minna; Lokki, Tapio; Sähkötekniikan korkeakoulu; Lokki, Tapio
The uses and services of communal libraries, as well as their soundscapes, have developed considerably during the past decades. Along with the changes, many libraries have become noisy and restless, as the acoustics of the space has not been adapted to the current situation. In this thesis the resulting acoustic problems were investigated and the solutions for them were given. The work was a part of the project Changing Soundscape of Communal Libraries where five libraries across Finland were studied. The acoustic problems in the libraries can be divided into five categories: sounds spreading from children and youth’s sections to other areas, sounds spreading from floor to floor, background noise level, reverberation and sound insulation. These properties were measured in each library and the results were compared to recommendations and the experiences of the library staff. In addition, a listening test was conducted to investigate the staff’s personal preferences on different acoustic environments. The vast majority of the results supported the existence of the problems above, for they differed from the recommendations or only barely fulfilled them. The listening test in turn confirmed that people prefer different acoustic environments in a library. However, the baseline for the solutions was to remove all the problems observed. The acoustics can be improved by controlling the reverberation and the spreading of sound. The libraries should add sound absorbing materials on for example walls and ceilings, place obstacles restricting the spreading of sound between sections, and raise the background noise level. Thick and well sealed structures or foldable walls would in turn be needed in the rooms with sound insulation requirements. The implementation of the solutions has to be planned for each library specifically since their facilities vary. All in all, the acoustics has not been properly taken into account in libraries. It affects the problems in the soundscapes and attention should be paid in designing it. A big change is indeed needed in the attitude: acoustics is an important part of the usability of a library and it should be a part of both new construction projects and renovations.
Acoustics in Green Buildings
(2023-01-23) Al-Ramadani, Hassan; Näveri, Nella; Möller, Henrik; Sähkötekniikan korkeakoulu; Lokki, Tapio
The past two decades have witnessed a dramatic rise in the number of green buildings in the construction industry; green buildings are certified through rating schemes, such as BREEAM and LEED, which consider acoustics part of Indoor Environmental Quality (IEQ). Although some studies have examined IEQ, there has been no research conducted in this field in Finland. This thesis compares acoustics criteria in BREEAM and LEED with Finnish national regulation and determines the challenges that acoustics consultants face in green buildings dealing with various design aspects. Additionally, the thesis evaluates the acoustics comfort of green office buildings by conducting a Post Occupancy Evaluation (POE) survey for the acoustics comfort on seven office green buildings and two office conventional buildings in Finland. Based on a literature review of earlier research, an online and paper-form survey was distributed to users of green buildings and conventional buildings. In addition, acoustics measurements were collected from the investigated buildings. An analysis of the responses demonstrated that users' satisfaction with acoustics comfort fluctuated within building categories regardless of the building being either green or conventional and it acquiring or missing acoustics credits. The results correspond to previous studies’ claims that acoustics comfort in green and conventional buildings is approximately the same. The survey indicates that personal and contextual variables influence acoustics comfort inside buildings (such as age, gender, building tenure, work desk conditions, and visual privacy); specifically, gender and visual privacy significantly impact acoustics comfort. Another finding is that acoustics measurements do not correlate with the survey results. This demonstrates that there are other aspects (such as personal and contextual variables) to consider for acoustics performance together with specified acoustics parameters by authorities or organizations.
Active Occlusion Cancellation for Hear-Through Headphones
(2019-06-17) Myöhänen, Lauri; Pakarinen, Jyri; Sähkötekniikan korkeakoulu; Lokki, Tapio
Hear-through headphones enable communication with other people without the need to remove the headphones. However, wearing headphones alters the user's perception of their own voice to be unnaturally loud at low frequencies due to the occlusion effect. The effect is caused by an increase in low frequency bone-conducted sound inside the ear canal. This thesis evaluates the use of analog feedback controller in order to perform active occlusion cancellation for in-ear headphones with hear-through functionality. In order to evaluate the effectiveness of the occlusion cancellation, sound pressure was measured in the ear canal under two settings: cancellation off and on. Effects of the cancellation on the hear-through equalization were also determined in free and diffuse field measurements. Analog feedback control is found to provide reduction in the occlusion effect in a frequency range of few hundred hertz. The frequency range is limited by the frequency-dependent phase shift occurring in the feedback loop. It was also found that the hear-through signal is amplified at the transition band of the analog controller. A digital and an analog filter was used to compensate for this amplification, both of which yielded similar results. This compensation is not performed for hear-through at low frequencies, since the attenuation also benefits the user by reducing external background noise.
Aistinvaraiset menetelmät konserttisalien äänenlaadun arvioinnissa
(2012-11-25) Jääskeläinen, Anna; Lokki, Tapio; Perustieteiden korkeakoulu; Immonen, Stina
Aistinvaraiset menetelmät konserttisalien akustiikan tutkimuksessa
(2009) Kuusinen, Antti; Lokki, Tapio; Elektroniikan, tietoliikenteen ja automaation tiedekunta; Eriksson, Jan
Akustiikkamateriaalien kulmariippuvainen äänenabsorptio
(2021-11-24) Cucharero Moya, Jose; Hänninen, Tuomas; Lokki, Tapio; Dept Signal Process and Acoust; Virtual Acoustics; Lokki Tapio group; Lumir Oy
Esittelemme tässä artikkelissa vaihtoehtoisen tavan mitata äänen absorptio-ominaisuuksia 2D-goniometrillä. Laitteistolla voidaan mitata materiaalin äänen absorptiokerroin äänen eri tulo- ja heijastuskulmilla. Menetelmä perustuu ensimmäisten heijastusten erotteluun muista häiritsevistä heijastuksista aikaikkunoinnilla. Menetelmän etuna on helppo näytteen valmistus, suhteellisen pieni näytekoko ja mahdollisuus mitata helposti perforoituja näytteitä. Menetelmällä saadut tulokset korreloivat hyvin jälkikaiuntahuone- ja impedanssiputkimittauksista saatuihin tuloksiin ja auttavat ymmärtämään materiaalien äänen absorptiota entistä laajemmin.
Akustiikkapäivät 2019: Oulu, 28. - 29.10.2019: Artikkelit ja ohjelma
(Akustinen Seura ry, 2019-10-28) Lokki, Tapio; Tietotekniikan laitos; Lokki Tapio group
Akustinen suunnittelu muistiystävällisessä asumisessa
(2021) Salminen, Viivi; Verma, Ira; Lokki, Tapio; Arkkitehtuurin laitos; Taiteiden ja suunnittelun korkeakoulu; School of Arts, Design and Architecture; Arpiainen, Laura
Muistisairaudet ovat ajankohtainen kansanterveydellinen ja -taloudellinen haaste. Muistisairauksien yleistyminen väestön ikääntyessä yhdessä ikä- ja palvelurakenteen muutoksen kanssa tekee muisti- ja ikäystävällisen suunnittelun kehittämisestä yhä keskeisempää. Muistisairaudet muuttavat aistikokemusta, mikä tekee aistien huomioimisesta olennaista muistiystävällisen ympäristön suunnittelussa. Ääniympäristö on yksi asumisen kehittämiskohteista. Esteetön kuunteluympäristö ja hyvä akustiikka tukevat muistisairaan henkilön jokapäiväistä elämää ja itsenäistä toimintaa. Tämä diplomityö tarkastelee muistisairaiden asumista ja hyvinvointia tukevan ääniympäristön suunnittelua. Opinnäyte on tehty osana SOTERA:n (Sosiaali- ja terveysalan rakentamisen tutkimus-ryhmä) MonIA-projektia (Monimuotoista integroitua asumista muistisairaille), jossa suunnitellaan ja tutkitaan uusia ja joustavia asumisratkaisuja kotona asumisen ja tehostetun palveluasumisen väliin. Tutkimuksen päätavoite oli kehittää olemassa olevin tietojen perusteella ohjeita muistisairaiden asumista ja hyvinvointia tukevan ääniympäristön toteuttamiseksi. Muita tutkimuksellisia päämääriä olivat tuoda ihmislähtöisempää näkökulmaa akustiseen suunnitteluun, huomioida asuinympäristön rooli osana hoitoa sekä tunnistaa muistisairaille suunnatun ympäristön erikoispiirteitä ja tarpeita muistiystävällisen ympäristön kehittämiseksi. Tutkimuksen teoriataustaa ja aineistokeruuta haettiin kirjallisuuskatsauksella. Aiheen monialaisuudesta johtuen kirjallisuuskatsaus käsitti tutkimusartikkeleita, raportteja ja kirjallisuutta useilta aloilta, mukaan lukien ympäristöpsykologia, arkkitehtuuri, akustinen suunnittelu ja neurotieteet. Diplomityö jakautuu tutkimus- ja suunnitteluosaan. Työ alkaa muistiystävällisen ääniympäristön ongelmien tutkimisella ja etenee analyysiluvun kappaleissa sen suunnittelussa huomioitaviin tekijöihin. Suunnitteluosassa tutkimusosan tietoa sovelletaan Helsingissä sijaitsevaan Laajasalon palvelutalon ääni- ja aistiympäristön kehittämisehdotukseen. Tutkimuksen perusteella asuinympäristöä voidaan muokata muistiystävällisemmäksi äänisuunnittelun keinoin. Työstä nousi esille ääniympäristön roolin tärkeys muistisairaan henkilön asuinympäristössä sekä sen moninaiset terveysvaikutukset. Tutkimuksen pohjalta kehitettiin muistiystävällisen ääniympäristön suunnittelun ohjetaulukko, joka perustuu tilatyyppeihin, sekä muistisairaille henkilöille olennaisiin ääniympäristön tekijöihin. Pääteemoiksi ääniympäristön suunnittelussa nousivat muistisairaiden henkilöiden osalta: yksilöllisyys, yhteisöllisyys, palauttavuus, turvallisuus, ja viihtyisyys. Lisäksi suunnitteluosuudessa tuodaan esille käytännön ratkaisuja, joilla kehittää olemassa olevien ja uusien rakennusten ääniympäristöjä.

Browsing by Author "Lokki, Tapio"

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