Browsing by Author "Jaatinen, Jussi"

Filter results by typing the first few letters
Now showing 1 - 5 of 5
  • Perävirtausammuksen laskentaympäristön kehittäminen
    (2003) Jaatinen, Jussi
     Helsinki University of Technology | Master's thesis
    Tässä työssä tarkastettiin aluksi TKK:n Aerodynamiikan laboratoriossa kehitetyn FINFLO- virtausratkaisijan toimivuus useiden versiopäivityksien jäljiltä. Tarkastus suoritettiin kuuden testitapauksen avulla, jotka kaikki liittyvät 155mm perävirtausammuksen virtauskentän tutkimiseen. Suoritettujen testien perusteella todettiin uusimman FINFLO-version 5.5.2 toimivan aivan yhtä hyvin kuin aikaisempi versio 5.1.1. Tämän lisäksi luotiin Linux-käyttöjärjestelmään mahdollisuus käyttää FINFLO-ohjelmaa sekä sen tulosten jälkikäsittelyssä että laskentahilojen tekemisessä tarvittavia ohjelmia. Työ piti sisällään FINFLOn 3D-koodin kääntämisen ja muokkaamisen siten, että se toimii lähdekoodin kääntämiseen valitun Intel Fortran -kääntäjän kanssa. Myös FINFLO Oy:ltä ostetut tulosten piirtämisessä tarvittavat Convergence- ja Draw-ohjelmat käännettiin ja muokattiin aerodynamiikan laboratorion FINFLO-ohjelmaan sopiviksi. Näiden lisäksi asennettiin kaupalliset Gridgen- ja Ensight-ohjelmat. Lopulta käännetyn ja asennetun FINFLO-ohjelman toimivuus tarkastettiin kahdella testitapauksella. Samalla suoritettiin myös nopeusvertailuja Linux- ja Silicon Graphics -koneiden välillä. Tehtyjen testilaskujen perusteella havaittiin Linux-Finflon toimivan moitteettomasti. Nopeusvertailut osoittivat uuden Linux-tietokoneen olevan noin kolme kertaa vanhaa tietokonekalustoa nopeampi. Kolmanneksi tässä työssä tutkittiin sekä pyörivän että pyörimättömän perävirtausammuksen virtauskenttää pienillä kohtauskulman arvoilla. Kohtauskulman arvoiksi valittiin 0°, 2° ja 4°. Vapaan virtauksen ammuksen halkaisijaan referoitu Reynoldsin luku oli 1,4- 10[6] ja Machin luku 1,2. Laskuja varten luotiin täysin kolmiulotteiden laskentahila, koska aksiaalissymmetriaoletus ei ole voimassa, kun kohtauskulma on nollasta poikkeava. Turbulenssimallien vertailemiseksi laskut suoritettiin käyttäen k-omega RCSST- ja EARS-mallia. Suoritettujen laskujen avulla voitiin ennustaa ammukseen vaikuttavat aerodynaamiset voimat kohtuullisen tarkasti. Myös pyörimisen ja kohtauskulman yhteisvaikutuksesta syntyvä Magnus-efekti voitiin ennustaa melko tarkasti. EARS-turbulenssimallilla nostovoimakertoimien arvot olivat samansuuruiset k-omega RCSST -mallin kanssa, mutta vastuskertoimen arvo oli kaikilla kohtauskulmilla huomattavasti pienempi kuin k-omega RCSST -mallilla. EARS-malli kuvaa vanaveden pyörteen hieman erilaiseksi kuin k-omega RCSST -malli, minkä takia myös painejakauma ammuksen perässä on erilainen. Tämä selittää vastuskertoimien erisuuruiset arvot. Tutkimus osoitti, että nykyisellä ohjelmalla voidaan laskea myös kohtauskulmalla olevan pyörivän perävirtausammuksen virtauskenttää, mutta laskuihin uhrautuu hyvin paljon aikaa.
  • Effect of inharmonicity on pitch perception and subjective tuning of piano tones
    (2022-08-01) Jaatinen, Jussi; Pätynen, Jukka
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The consensus in piano tuning philosophy explains the stretched tuning scale by the inharmonicity of piano strings. This study aimed to examine how variable inharmonicity influences the result of the piano tuning process, compare the tuning curves of aurally tuned pianos with the curves derived from subjective octave enlargement experiments, and evaluate whether the pitches of inharmonic or harmonic versions of the same tone are perceived differently. In addition, the influence of strings of other piano keys on the measured inharmonicity of a single piano string was investigated. The inharmonicity of all individual strings was measured on a Steinway D grand piano. Variable inharmonicity was implemented by additive synthesis with frequency-adjusted sinusoidal partials. Fifteen piano tuners and 18 orchestra musicians participated in the experiments. The results indicate that the inharmonic piano tones produced a keyboard tuning curve similar to the Railsback curve and differed significantly from the harmonic counterpart. The inharmonic tuning curve was reminiscent of the subjective octave enlargement curve. Inharmonic tone pitches were perceived to be higher than harmonic tones up to C » 7. The covibrating strings of the other keys did not exhibit any meaningful effect on the measured inharmonicity of a single string of the played key.
  • Electronic Hearing Protection for Musicians
    (2017-07) Albrecht, Robert; Jaatinen, Jussi; Lokki, Tapio
     A4 Artikkeli konferenssijulkaisussa
    Many people are exposed to large sound pressure levels ei- ther occasionally or regularly, and thus need to protect their hearing in order to prevent hearing loss and other hearing disorders. Earplugs are effective at attenuating sound from the environment, but they do not attenuate bone-conducted sound, but instead amplify it at low frequencies due to the occlusion effect. This is a problem, e.g., for many mu- sicians and especially wind instrument players, since this low-frequency amplification greatly affects the sound of their own instruments. This makes it difficult for the musi- cians to play while using hearing protectors, and therefore many musicians choose not to use hearing protectors at all. In this paper, we propose electronic hearing protectors that mitigate the problems associated with musicians’ hearing protection through several different approaches: reduction of the occlusion effect, adjustable attenuation with natural timbre, and monitoring of the musician’s own instrument. We present the design of prototype electronic hearing pro- tectors and the evaluation of these by professional musi- cians, where they were shown to alleviate the problems as- sociated with conventional hearing protectors.
  • Octave stretching phenomenon with complex tones of orchestral instruments
    (2019-11-01) Jaatinen, Jussi; Pätynen, Jukka; Alho, Kimmo
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    For decades, the phenomenon of subjectively enlarged octaves has been investigated using sinusoidal and synthesized complex tones. The present study elaborates the topic with samples of real orchestra instruments in successive tone listening experiments. Compared to previous research, this study also included a substantially larger number of subjects (N = 36). Examined instrument tones were categorized into five groups based on their acoustic principles. In addition, each group was assessed at three dynamic levels (pp-mf-ff). Collected data were analyzed with tuning stretch curves by applying generalized additive models in the manner of the Railsback curve used to characterize piano tuning. Although the tuning curve modeled for the orchestra instruments was observed to differ slightly from the Railsback curve and typical Steinway D grand piano tuning (Steinway, New York), the stretching trends were qualitatively similar. Deviation from a mathematical equal-tempered scale was prominent. According to statistical analyses, dynamics or musical background of the participant did not affect results significantly, but some instrument groups exhibited differences in the curve extremities. In conclusion, the stretched scale is natural for a human listener and should be used as a reference scale in tuning machines instead of the mathematical equal-tempered scale.
  • Uncertainty in tuning evaluation with low-register complex tones of orchestra instruments
    (2021-11-19) Jaatinen, Jussi; Pätynen, Jukka; Lokki, Tapio
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The relationship between perceived pitch and harmonic spectrum in complex tones is ambiguous. In this study, 31 professional orchestra musicians participated in a listening experiment where they adjusted the pitch of complex low-register successively presented tones to unison. Tones ranged from A0 to A2 (27.6–110 Hz) and were derived from acoustic instrument samples at three different dynamic levels. Four orchestra instruments were chosen as sources of the stimuli; double bass, bass tuba, contrabassoon, and contrabass clarinet. In addition, a sawtooth tone with 13 harmonics was included as a synthetic reference stimulus. The deviation of subjects’ tuning adjustments from unison tuning was greatest for the lowest tones, but remained unexpectedly high also for higher tones, even though all participants had long experience in accurate tuning. Preceding studies have proposed spectral centroid and Terhardt’s virtual pitch theory as useful predictors of the influence of the envelope of a harmonic spectrum on the perceived pitch. However, neither of these concepts were supported by our results. According to the principal component analysis of spectral differences between the presented tone pairs, the contrabass clarinet-type spectrum, where every second harmonic is attenuated, lowered the perceived pitch of a tone compared with tones with the same fundamental frequency but a different spectral envelope. In summary, the pitches of the stimuli were perceived as undefined and highly dependent on the listener, spectrum, and dynamic level. Despite their high professional level, the subjects did not perceive a common, unambiguous pitch of any of the stimuli. The contrabass clarinet-type spectrum lowered the perceived pitch.