Abstract: Aspects of embodiments concerns an apparatus for tuning a drum, the drum comprising a drum shell having an upper skin, the apparatus comprising: an outer static rim that is removably operably coupleable to the inside wall of a drum shell; a diameter adjustment mechanism that is removably operably coupleable with the drum shell, the diameter adjustment mechanism including one or more inner cylindrical shells mountable within the drum shell and being configured for axial displacement whereby an upper rim thereof can be selectively brought into or out of contact with an upper skin of the drum and thereby change an effective diameter of the upper skin.

Abstract: Aspects of embodiments concerns an apparatus for tuning a drum, the drum comprising a drum shell having an upper skin, the apparatus comprising: an outer static rim that is removably operably coupleable to the inside wall of a drum shell; a diameter adjustment mechanism that is removably operably coupleable with the drum shell, the diameter adjustment mechanism including one or more inner cylindrical shells mountable within the drum shell and being configured for axial displacement whereby an upper rim thereof can be selectively brought into or out of contact with an upper skin of the drum and thereby change an effective diameter of the upper skin.

Abstract: A controllable buoyant system (10) includes a support structure having a sealed hollow enclosure (12) containing a first gas and surrounded by a second gas, either the first gas or the second gas being lighter than ambient air. The hollow enclosure is pre-filled with the first gas via a one-way valve that prevents the first gas escaping and an altitude sensor (14) generates an altitude signal indicative of a height of the support structure. A height transducer (17, 21, 61, 66, 67, 68) coupled to the hollow enclosure is responsive to the altitude signal for varying the buoyancy of the support structure. A controller (15) is coupled to the altitude sensor and to the height transducer and is responsive to the altitude signal and to at least one reference altitude signal for automatically controlling the height transducer in order to maintain the support structure buoyant at the preset altitude.

Abstract: A controllable buoyant system (10) includes a support structure having a sealed hollow enclosure (12) containing a first gas and surrounded by a second gas, either the first gas or the second gas being lighter than ambient air. The hollow enclosure is pre-filled with the first gas via a one-way valve that prevents the first gas escaping and an altitude sensor (14) generates an altitude signal indicative of a height of the support structure. A height transducer (17, 21, 61, 66, 67, 68) coupled to the hollow enclosure is responsive to the altitude signal for varying the buoyancy of the support structure. A controller (15) is coupled to the altitude sensor and to the height transducer and is responsive to the altitude signal and to at least one reference altitude signal for automatically controlling the height transducer in order to maintain the support structure buoyant at the preset altitude.

Abstract: An object is supported freely in space without requiring an anchoring point connected to ground, by attaching the object to a support structure adapted to float in air when filed with a gas having lower specific gravity than air at a controlled pressure that provides sufficient buoyancy for different weight objects. The support structure is released together with the attached object so as to reach an equilibrium position where a buoyancy force of the support structure counteracts a combined weight of the enclosure and attached object. The object may be integral with the support structure and may be a self-powered electrical device operating on a battery or solar energy. The enclosure may be a floating platform or may be part of an object.