A reliable source of information on state-of-the-art automotive technology for more than 80 years already. Images Image information. Download image. Collect image. The Bosch Automotive Handbook is widely regarded around the world as a standard work for automotive technology. Attenuation of acoustic emissions: Reduction in the primary mechanical or electrodynamic generation of structure-borne noise and flow noises; damping and modification of sympathetic vibrations; reduction of the effective radiation surfaces; encapsulation.
Application of simulation techniques modal analysis, modal variation, finite-element analysis, analysis of coupling effects of airborne noise for advance calculation and optimization of the acoustic properties of new designs. Sound field quantities are normally measured as RMS values, and are expressed in terms of frequency- dependent weighting A-weighting.
This is indicated by the subscript A next to the corresponding symbol. The sound power of a sound source is described by the sound power level Lw. Sound power cannot be measured directly.
It is calculated based on quantities of the sound field which surrounds the source. Measurements are usually also made of the sound pressure level Lp at specific points around the source see DIN 45 Lw can also be calculated based on sound intensity levels LI measured at various points on the surface of an imaginary envelope surrounding the sound source.
The sound pressure level is ten times the logarithm to the base 10 of the ratio of the square of the RMS sound pressure to the square of the reference sound pressure. The sound intensity level is equal to ten times the logarithm to the base ten of the ratio of sound intensity to reference sound intensity.
If two independent sound fields are superimposed, their sound intensities or the squares of their sound pressures must be added. The overall sound level is then determined from the individual sound levels as follows:. The noise measurements employed to monitor compliance with legal requirements are concerned exclusively with external noise levels. The vehicle approaches line AA, which is located 10 m from the microphone plane, at a constant velocity.
Upon reaching line AA, the vehicle continues under full acceleration as far as line BB also placed 10 m from the microphone plane , which serves as the end of the test section.
The noise- emissions level is the maximum sound level as recorded by the microphone 7. Passenger cars with manual transmission and a maximum of 4 forward gears are tested in 2nd gear. Consecutive readings in 2nd and 3rd gear are employed for vehicles with more than 4 forward gears, with the noise emissions level being defined as the arithmetic mean of the two maximum sound levels.
Measurements are taken in the vicinity of the exhaust muffler in order to facilitate subsequent testing of motor-vehicle noise levels. Once the engine speed levels off, the throttle valve is quickly returned to its idle position. The recorded level is entered in the vehicle documentation in dB A with the suffix "P" making it possible to distinguish between this figure and levels derived using earlier test procedures.
No legal maxima have been specified for standing noise levels. There are no legal requirements pertaining to interior noise levels. The interior noise is measured, e. One series of measurements is always to be made at the driver's seat; other measurement locations are selected in accordance with the passenger seating arrangement inside the vehicle.
There are no plans to introduce a single value for indicating inside noise levels. Higher limits are valid for off-road and 4WD vehicles. Supplementary noise limits apply for engine brakes and pneumatic equipment. The effect of noise on the human being is evaluated using the rating sound level Lr see also DIN 45 This is a measure of the mean noise immission over a period of time e.
Noise immission parameters such as pulsation and tonal quality can be taken into account through level allowances see table below for reference values. The following guideline values for the rating sound level Germany; Technical Instructions on Noise Abatement, 16 July are measured outside the nearest residential building 0.
In the case of noises which fluctuate in time, the mean A-weighted sound pressure level resulting from the individual sound pressure levels and the individual exposure times, equals the equivalent continuous sound level if it describes the mean sound energy over the entire assessment time period see DIN 45 The human ear can distinguish approximately levels of acoustic intensity and Thus there is not necessarily any direct correspondence between perceived noise levels and energy- oriented technically-defined sound levels.
A rough approximation of subjective sound-level perception is provided by A-weighted sound levels, which take into account variations in the human ear's sensitivity as a function of frequency, the phon unit and the definition of loudness in sone. Sound-level measurements alone do not suffice to define the nuisance and disturbance potential of noise emanating from machinery and equipment.
A hardly-perceptible ticking noise can thus be perceived as extremely disturbing, even in an otherwise loud environment. The loudness level is a comparative measure of the intensity of sound perception measured in phon. The loudness level of a sound pure tone or noise is the sound pressure level of a standard pure tone which, under standard listening conditions, is judged by a normal observer to be equally loud.
The standard pure tone is a plane sound wave with a frequency of Hz impinging on the observer's head from the front.
A difference of 8 to 10 phon is perceived as twice or half as loud. The standard pure tone judged as being equally loud has a specific sound pressure level in dB. This value is given as the loudness level of the tested sound, and has the designation "phon". Because human perception of sound is frequency-dependent, the dB values of the tested sound for notes, for example, do not agree with the dB values of the standard pure tone exception: reference frequency Hz , however the phon figures do agree.
See the graph below for curves of equal loudness level according to Fletcher-Munson. Allocation of sounds to objective and subjective scales, curves of equal loudness level, weighting curve A of sound-level meter. The sone is the unit employed to define subjective noise levels.
The starting point for defining the sone is: How much higher or lower is the perceived level of a particular sound relative to a specific standard. Doubling or halving the loudness is equivalent to a variation in the loudness level of approx. There is an ISO standard for calculating stationary sound using tertiary levels Zwicker method.
This procedure takes into account both frequency weighting and the screening effects of hearing. The spectrum of perceptible sound can be divided into 24 hearing-oriented frequency groups bark.
The groups define perceived pitch levels. Modeling of forces acting during operation enables calculation of operational vibration shapes. Thus optimization of design with regard to vibrational behavior. Air-borne noise, fluid-borne noise: Sound-field calculation e.
This is the evaluation, predominantly by human testers, of noise and interference levels and the classification of operating defects based on audible sound or structure-borne noise as part of the production process, e. Automated test devices are used for specialized applications, but they are at present still unable to achieve human levels of flexibility, selectivity and learning ability.
Advances have been made through the use of neural networks and combined evaluation of sound properties. Specific configuration of operating noises by means of design measures; subjective aural impressions and psychoacoustics are taken into consideration. The objective is not primarily to reduce noise but rather to achieve a general sound quality, to embody specific features e. See quantities and units for names of units, see Conversion of units of temperature for conversion of heat units and Properties of materials for thermal expansion, heat of fusion, heat of evaporation.
Thermal conduction: Heat is conveyed inside a solid, liquid or gaseous body by contact between the particles. Convection: Heat is conveyed by the particles of a moving liquid or gaseous body. In natural or free. Radiation: Heat is transferred from one body to another by electromagnetic waves without a material carrier.
Empty space and air are pervious to thermal radiation. Solid bodies and most liquids are impervious to thermal radiation, as are various gases to certain wavelengths.
Black-body radiator1 1. Copper, oxidized 0. An example of a black-body radiator is the opening in a carbon tube. Measurement rangeMethod of operation Examples of application Liquid-in-glass thermometers Thermal expansion of the liquid is visible in For liquids and gases, for monitoring a narrow glass tube.
Liquid: Pentane — steam, heating and drying systems; — Alcohol — Mercury — Pressure-spring thermometers Due to its expansion pressure mercury, For monitoring and recording toluene or vapor pressure ether, hexane, temperatures including remote — Solid expansion thermometers Different thermal expansion of two metals Bimetallic thermometers Curvature of a strip consisting of two — Resistance thermometers Change in resistance caused by change in Temperature measurements on temperature.
Platinum wires — Remote transmission Thermistors Sharp drop in electrical resistance as the Measurement of minor temperature Temperature measurements on and in Thermoelectromotive force of two metals — Remote whose junctions are at different temperatures. Radiation thermometers pyrometer, infrared camera, high-speed pyrometer The radiation emitted by a body isan Melting and annealing furnaces. It is sensed by Surface temperatures. Emissions level must be observed.
Temperature-sensitive paints, temperature-indicating crayons Color changes when specific temperatures Temperature measurements on rotating are exceeded. Paints and crayons are parts, in inaccessible places, in machin- The new color remains after cooling.
Suction thermometers, pyrometers Measurement of flame tem-perature Other temperature-measurement methods: spectroscopy, interferometry, quartz thermometry, noise thermometry, liquid crystals, acoustic and magnetic thermometers.
Energy can be neither created nor destroyed. Only the form in which energy exists can be changed, e. Heat cannot be completely converted to another form of energy, e. It is a veritable fountain of knowledge in easy to understand terms. We highly recommend it for every enthusiasts automotive reference library. Added to Your Shopping Cart. Books Video icon An illustration of two cells of a film strip. Video Audio icon An illustration of an audio speaker.