With the popularity of immersive media, developing usable tools for content development is important for the production process. In the context of 3D audio production, user interfaces for authoring and editing 3D audio trajectories enable content developers, composers, practitioners, and recording and mixing engineers to define how audio sources travel in time. However, common interaction techniques in 3D audio production tools can make the workflow of this task tedious and difficult to accomplish. This study investigates this problem by classifying the atomic tasks (spatially and temporally) of a general composite task of authoring 3D audio trajectories and then evaluating different interaction techniques across these tasks. Common graphical user interfaces were compared with input devices having varying degrees-of-freedom for spatial atomic tasks in order to investigate the effect of direct manipulation and integrality of interaction techniques. Continuous and discrete interaction techniques were compared for temporal tasks in order to investigate the effect of direct manipulation. Results suggest that interaction techniques with high degrees of integrality and direct manipulation reduce task completion time compared to standard GUI techniques. The design of temporal tasks can create a visual bias, and discrete-time controls can be a suitable method for traversing a small number of control points. These results and further observations provide directions on the study of interaction technique design for 3D audio tools, which in turn should improve workflows of 3D audio content creation.

International audience3D audio production tools vary from low-level programming libraries to higher-level user interfaces that are used across a wide range of applications. However, many of the user interfaces for authoring 3D audio parameters are underdeveloped, forcing users to resort to ad hoc solutions with other tools or programming languages. Identifying these limitations and custom methods are needed to inform the development of new user interfaces. Towards this end, an on-line survey was conducted with current practitioners to gather ethnographic information on their tools, methods, and opinions. Results of the survey revealed specific methods and limitations within authoring techniques and 3D audio production with regards to Audio Rendering and Recording, Visual Feedback, Functionality, and Workflow Integration. These results also shed light on three basic tasks that have to be performed interactively with 3D audio production tools: Defining the Rendering Space, Creation and Manipulation of Audio Objects, and Monitoring with Audio/Visual Feedback. This classification helps identifying the needs for 3D audio tools that address issues within the workflow and low-level functionality of systems

The sound radiation pattern of a grand piano is highly complex and depends on the shape of the soundboard, construction of the frame, reflections from the lid and other parts of the instrument's structure. The spectral energy generated by and emitted from the instrument is further complicated by the sound production mechanism (hammers, strings), the attack velocity, and results in independently complex behaviors depending on the register of the piano. This paper presents the acoustic measurements of the radiation pattern of a grand piano using a high spatial resolution measurement technique. Measurements of a Yamaha Diskclavier were taken using a 32-channel microphone array with a 2-inch spacing between capsules. The complex radiation patterns and overtone structure is analyzed for middle-C at three attack velocitiespianissimo, mezzo forte, and forte. Comparisons of the effect of attack strength on frequency response and radiation pattern are presented. INTRODUCTIONThe piano is a complex instrument. Capturing the sound and character of this large and complex instrument has been the subject of much debate for audio engineers. The piano's complexities are a result of the many physical and acoustical components and properties that directly affect the propagation of sound and the spatial radiation pattern of the instrument. In addition to the many physical components that make up the instrument (e.g. soundboard, frame, hammers, strings, etc.), the manner in which a piano key is struck has a significant impact on its spectral characteristic. To produce a sound, a key on a piano is pressed, the hammer lifts and strikes the string. The vibrations on the string are amplified by the soundboard and propagate through the body of the instrument. This process is further complicated by the fact that there may be sympathetic vibrations from strings other than the one that was excited. The velocity of a key determines the force from the hammer onto the strings. This force not only vibrates its intended string, but excites other portions of the piano as well. To gain an understanding of how the strength, or velocity, of the attack of a single note affects the spectral content and spatial distribution of the energy around a piano, we measured the spectral radiation pattern of the piano using keystrokes with various levels of attack strength.In this paper, we present the acoustic measurement and analysis of a densely sampled radiation pattern of the Yamaha Disklavier grand piano. Spectral characteristics are analyzed for middle C (C4), across the top of a lidless Yamaha Disklavier grand piano for three different velocities. The results of the fundamental frequency and four overtones are presented and compared against other velocities, providing insight to how the spectral and spatial distribution of the harmonic changes as a function of attack strength, and the resulting non-linearities in spectral content that arise.

A variable gain, zero offset, dc coupled video amplifier has been developed which uses a recently introduced ±5 V operational amplifier with 1.6 GHz gain-bandwidth product. The amplifier is inexpensive and it is particularly suited for amplifying the outputs of microwave diode detectors and driving 50 Ω loads. The large input bias currents of wideband operational amplifiers increase the sensitivity of positive polarity diode detectors, but they decrease the sensitivity when a negative polarity diode detector is used at the amplifier input. To eliminate this effect, matched N-channel junction field-effect transistors (JFETs) are used to buffer the operational amplifier inputs, which reduces the input bias current to ∼1 pA. An added benefit of the JFETs is that the amplifier offset voltage is unaffected by changes in gain or source impedance. Once the offset is zeroed out, it remains zero for all gains and for any combination of diode detectors connected at the input. The maximum attainable gain-bandwidth product is somewhat lower with the JFETs (typically 400 MHz), but the amplifier operates reliably for gains up to 40–50 dB.