The Precedence Effect (Hass effect)

Haas Effect.. A technique used in audio production to obtain a wide, spacious and open sound during editing. A good video and post worth reading!

Andreas Valiantis

Almost everyone knows that the early cartoons where made by different pictures changing at small intervals. The impression of movement is made by the ability of the eye to integrate the pictures arriving in the eye within a small period of time which is at least 16 pictures per second. Similar to eyes, ears can integrate a sound that comes within 35ms after the direct sound.  For example if someone sits in a room and experience a single pulse as a direct sound and a reflection sound within 35ms, the ear will perceive the sound as one. The problem is if the direction of the direct and the reflected sounds are different from which direction the listener will experience the source coming? The answer is that the sound which arrives first establishes the perceptual source location of later sounds. This is called Haas effect, precedence effect or law of the first…

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Sonodyne

Fancy buying a set of monitor speakers but unsure where to start? Why not try reading this wonderful post regarding Sonodyne speakers by Sarah De Warren 🙂

Sarah de Warren

sonodyne_sm100ak 

Sonodyne 100AK – I highly recommend this bit of equipment.

Pro-audio equipment designed in India is yet to break into the Western market. However, I think Sonodyne speakers may be the thing to change this. Having bought two SM 100AK monitors from Absolute Music in August, I am a big fan – they sound amazing.

The company is engineering and research lead, based at a factory in Kolkata, launched in the 1960s by Ashoke Mukherjee. Providing both professional and consumer audio solutions, they have now started distributing farther afield than just India.. to places such as America and the UK. I was probably one of the first UK buyers.

The cabinets are made out of die-cast aluminium, with limited cabinet-induced resonance and non-parallel interior design, which eliminates the effect of standing waves. The edges of the cabinet are rounded to reduce edge diffraction and turbulence.

The low frequency response is punchy and sounds amazing…

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Fact or Fiction?: A high pitch and piercing voice can shatter a window glass

Have you ever watched a film/movie whereby a glass window is broken through the vocal sound? Is it really possible?

Before answering the question, lets look through the cause of it. A glass is able to be broken through sound waves via resonance. So what is resonance? According to hyperphysics, a resonant frequency is a natural frequency of vibration determined by the physical parameters of the vibrating object. Resonance can be a good or bad thing to us depending on the application that is used on. A scenario where it is good to us is when one plucks the string of an acoustic guitar, the vibration of the string enters the sound hole and gets reflected in the inner portion of the guitar before being amplified. In another scenario where it is bad to us is when a bridge resonant frequency is being hit, it will cause the bridge to vibrate tremendously and even collapse just like the figure shown below.

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Fig 1. Resonance on a bridge (http://science.howstuffworks.com/engineering/civil/bridge10.htm)

Now back to the main question. I am sad to say that it is not possible to break with just vocals alone. The large sound pressure level of the natural frequency (varies depending on the density of the glass) is required from the vocals in order to shatter it. 🙂

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Fig 2. Shattering of glass (http://massagetherapy.careerpathblog.com/tag/shatter-glass/)

 

References

(1) Resonance

http://hyperphysics.phy-astr.gsu.edu/hbase/sound/reson.html

(2) Can a singer breaks a glass?

http://www.livescience.com/37005-singer-break-glass-singing-break-wineglass.html

Sound Localisation

Human ears are a unique pair of organs to look into. Without opening our eyes, we are able to detect sound from various positions around us. Being able to localize sound enables us to detect a vehicle approaching without the need for us to turn our head. Imagine a sound source is on the right hand side of you, sound will reach your right ear before the left ear. Also, the sound from the right ear has a higher level than the left ear because the head shadows the left ear.

There are two main ways for our ears to localize sound.

(1)Interaural Time Differences (ITD)

(2)Interaural Level Differences (ILD)

Low frequency sound which is approximately below 1500Hz gives rise to ITD.  In contrast, high frequency sound which is approximately above 1700Hz gives rise to ILD. This is because our head acts like a low pass filter and much of the high frequency sound gets reflected off thus reducing the sound levels being reached to the other ear. These mentioned frequencies vary as the size of the head differs from one person to another. For frequencies in between 1500Hz and 1700Hz, both roles ITD and ILD play a part in being able to localize sound.

Knowing the fundamental of sound localization, it is possible to use this critical information in audio production. In stereo recording, both panning and level are used to simulate a real live band performing in front of us.

Youtube is a good website to find some audio and acoustics related stuffs. Some of the users provide an easy way to understand the materials so that you would have some idea about it. The video below explains and demonstrate how sound localization is being tested.

Do you agree with my blogpost?  Feel free to comment it. 🙂

 

References

(1)  Sound Localization

http://www.open.edu/openlearn/science-maths-technology/science/biology/hearing/content-section-12.1

(2) Perception

http://www.lifesci.sussex.ac.uk/home/Chris_Darwin/Perception/Lecture_Notes/Hearing5/hearing5.html

Hypersonic sound

I’ve found an interesting video link in TED website which is related to audio. It is an approximately 15minutes video which explains about hypersonic sound. Loudspeakers tend to be poor in its directivity. However hypersonic sound is able to control and focus the sound to where the user wants it to be. A good analogy would be light bulb. Light bulb tends to emit light in all directions. We call this an unfocused light as it is perfectly diffused in all directions. However, when a reflector is placed behind the light bulb, it is able to focus the light towards the front of the lightbulb. Woody Norris has invented a loudspeaker which is able to focus sound directly in front of the loudspeaker. In his video, he shares more about how his invention works and the theory behind it.

I will highly recommend everyone to watch this video. 🙂

Sonic the Hedgehog (Supersonic)

For those who don’t know Sonic the hedgehog, he is an animated character who has the ability to run at supersonic speed. Have you ever heard of supersonic speed? It is the speed that is faster than the speed of sound in air which is approximately 343m/s. Some of the fastest airplanes are U.S Navy F/A 18, F-111 Aarkvark, F-15 Eagle, etc.

In relation to my Doppler effect blog post, a person on the ground would hear a high frequency noise as a commercial plane is approaching and a low frequency noise when the plane flies past him/her. However when an airplane breaks the sound barrier and flies faster than the speed of sound, he/she would hear a sonic boom which is a loud noise like thunder. Pressure wave fronts are formed at the front and back of an airplane. At supersonic speed, both the pressure wave fronts will be forced to merge together to form a large single wave. Therefore all the sound waves that would have normally propagated ahead of the plane are then combined together so at first one would hear nothing, and then one would hear the boom it creates. You can learn more about sonic booms by imagining the ripples that a boat leaves in the water.

At times, it is possible to see a cone-shaped clouds occurring behind the airplane. It is reacting to the temperature and pressure change induced by the airplane’s body by sliding past.

Do you agree about what I have written about supersonic speed? Feel free to make a comment about my blog post. 🙂

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Fig 1. A bullet traveling faster than the speed of sound in air.

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Fig 2. Cone-shaped clouds formed behind the aircraft.

 

References

The 10 fastest Military Airplanes.

[1] http://www.livescience.com/39829-fastest-military-airplanes.html

What is supersonic flight?

[2] http://www.nasa.gov/audience/forstudents/k-4/stories/what-is-supersonic-flight-k4.html#.U1ocbRb-uZw

Video of supersonic.

[3] https://www.youtube.com/watch?v=gWGLAAYdbbc

What causes a sonic boom?

[4] http://science.howstuffworks.com/question73.htm

Picture of a bullet traveling faster than the speed of sound in air.

[5] http://www.nasa.gov

Why do airplanes leave tracks in the sky?

[6] http://wonderopolis.org/wonder/why-do-airplanes-leave-tracks-in-the-sky/

Back to Basic (Waves)

What is acoustics? In a nutshell, it is the physics of sound. In acoustics, we deal a lot with waves. Waves?? Isn’t that a boring topic to learn? It’s just particles oscillating in space. Let me share with you how waves impact our life. Lets start with the basic question “What is a wave?”. Well a wave is an oscillation that travels through a medium. A wave can be longitudinal or transverse depending on the direction of its propagation. Now I am not going to bore you with all the physics and theory about waves. You can just Google them to know more about it.

Waves are used widely in all aspect of life. Firstly, human audible hearing range is taken approximately 20Hz to 20kHz.  For instance, we are able to hear the sound waves that is emitting from a loudspeaker. Frequencies lower than the audible hearing range are called infrasound whilst above it is called ultrasound.  Infrasound waves can be used to monitor earthquake or petroleum formations below the earth. On the other hand, ultrasound waves can be used for animal, chemistry, medical, destructive and others.  One of the many wonderful things ultrasound wave is able to do is to detect pregnancy. Lastly not to forget about sonar waves. They are used widely for underwater acoustics. It is a sound propagation used to navigate, communicate with or detect objects on or under the surface of the water.

Image

http://en.wikipedia.org/wiki/File:Ultrasound_range_diagram.svg

So the next time you think about how dull waves are, do think about the many wonders it can do in our life.  🙂

 

Reference:

[1] http://www.physicsclassroom.com/class/waves/Lesson-1/What-is-a-Wave