Acoustics

**__ Acoustics __**


**- Speed:** distance travelled in unit time. (m/s)

**- Frequency:** is the number of waves that pass a point per second. It is meassured in Hertz.

**- Wavelength:** is the distance between matching points on a wave. Sometines its called Lambda and it is meassured in metres.

**- Longitudinal:** vibration parallel to direction of travel of wave.

**- Transverse:** vibration at right angle to direction of travel of wave.

**Notes:** ( video: **Sound** Waves And Their **Sources)**

Vibrations, are invisible waves in the sourrounding air.

- Each movement of vibrations sets up new disturbance or soundwave impulses.

- We can asume that waves are transmited by air molecules.

- In one complete vibration, sound travels a distance of 1 wavelength.

- An Oscillograph, helps to record preasure variations of soundwaves.

- Loudness, pitch and quality are three auditorial effects of musical sounds.

**-** Loudness: every sound sets up a disturbance in the transmiting media. The larger de disturbance are displacements of the individual particles, the greater ir the wave above the neutral line. This displacement is called amplitude.

- Pitch: the auditory effect of frecuency. The greater de frecuency, the higher the pitch.

- In an instrument, each vibrating string is made to produce diferent tones.

- Differences on the audible component of a sound determine its quality. Quality helps us recognize the caracteristic sounds of various musical instruments and distinguish one voice from another.

- There are also vibrating surfaces. The vibrations from such diafragms are often quite complex.

- Another source of sounds is the vibrating columns of air.

- In an organ, the wavelength in the shorter pipes are shorter and their frecuencies are greater than the longer pipes.

- The vocal mecanism of man also depends on the mechanism of a column of air.





NOTES:

- Sound transmission, sound absorption, sound reflection and sound diffusion are all aspects that are important in a room’s acoustics. **-** Room acoustic descriptors can be used to formulate room acoustic specifications and to check the effect of different procedures. These includes: **Reverberance**, wich is linked to the speed at which sound energy disappears in a room. **Speech clarity,** it concerns the quality of speech transfer to the listeners. **Auditory strength,** is the level at which we experience sound. **Spatial decay,** the sound level decreases as the distance from the sound source increases. The design of the room, influences the extent to which the sound level decreases along with the distance. **- Sound insulation:** It describes any attempt to isolate, or soundproof, an environment from outside noise. **- Different acoustic room types:** **Hard rooms:** is a room with little sound absorption, in which the surfaces reflect most of the noise. **Rooms with absorbent ceilings:** is much more common, is a room with a sound-absorbing ceiling. This type acts differently than the hard room and, as a rule, requires several descriptors for an acoustic assessment. **Open-plan rooms:** is a room with extended forms, such as open-plan areas and corridors. These are an example of room design where the reverberation time must be supplemented with descriptors. **- Room Acoustic Planning**: It is vital to clearly specify your requirements for room acoustic quality early on in the building process.Depending on what will be going on in the rooms, room acoustic properties such as sound level, reverberance or speech clarity may need to be given different priority. - The reverberation time depends not only on absorption, but also furnishings, the location of the absorbers and the shape of the room. - The more absorption in the room, the lower the sound level. - Despite having the same reverberation time, rooms can subjectively be perceived differently. - **Airborne sound**, is directly transmitted from a source into the air. It’s all sound that reaches your ear. **- Structure-borne sound,** also known as "impact noise," is sound that travels through solid building materials such as footsteps on floors, door slams, plumbing and mechanical equipment vibrations, and the impact of rain and weather on a building.