Mindblown: a blog about philosophy.

Vibration problems are solved by considering the system as a number ofsprings and masses with damping. It is sometimes possible to reduce theproblem to a single mass supported by a spring and a damper. If the vibration is produced by a motor inside a machine, it is usuallydesirable to ensure that the frequency of motor…

Vibration is monitored with an accelerometer. This is a device that issecurely attached by some means to the surface under investigation. Theaccelerometer produces a tiny electrical charge output, proportionalto the surface acceleration, which is then amplified by a chargeamplifier and recorded or observed with a meter. The frequencies ofinterest are generally lower than sound, and…

When something oscillates about a static position it can be said tovibrate. The vibration of a speaker diaphragm produces sound, butusually vibration is undesirable. Common examples of unwanted vibrationare the movement of a building near a railway line when a train passes,or the vibration of the floor caused by a washing machine or spindryer. Floor…

Loudness is the human impression of the strength of a sound. Theloudness of a noise does not necessarily correlate with its soundlevel. Loudness level of any sound, in phons, is the decibel level ofan equally loud 1kHz tone, heard binaurally by an otologically normallistener. Historically, it was with a little reluctance that a simplefrequency weighting…

The speed of sound in air at a temperature of 0 degC and 50% relativehumidity is 331.6 m/s. The speed is proportional to the square root ofabsolute temperature and it is therefore about 12 m/s greater at 20degC. The speed is nearly independent of frequency and atmosphericpressure but the resultant sound velocity may be substantially…

Sound power level, Lw, is often quoted on machinery to indicatethe total sound energy radiated per second. The reference power istaken as 1pW. For example, a lawn mower with sound power level 88dB(A) will producea sound level of about 60dB(A) at a distance of 10 metres. If the soundpower level was 78dB(A) then the lawn…

The way sound changes with distance from the source is dependent on thesize and shape of the source and also the surrounding environment andprevailing air currents. It is relatively simple to calculate providedthe source is small and outdoors, but indoor calculations (in areverberant field) are rather more complex. If the noise source is outdoors and…