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What is Jitter? What is a more stable voice?

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Jitter is a measure of the irregularities in the frequency at which the vocal cords vibrate. Even when one tries hard to sing a particular note and keep it at a constant pitch, there will always be slight irregularities in the speed at which the vocal cords are vibrating and hence the pitch over time. Singers can sometimes notice this when they’re tired for example. With training, singers work to minimize these irregularities, or Jitter, in their voice. There are several ways to calculate the magnitude of the Jitter and this is measured in OperaVOX as the percentage change in the frequency of consecutive vocal cord vibrations from their common average. The higher the Jitter and the more abnormal the voice sounds. High values of jitter (in excess of 1 or 2%) can indicate a problem with your voice such as throat inflammation for example. High Jitter can be caused by a number of conditions that affect the vocal cords. If you are a singer, you will want a very stable voice and therefore very low jitter measurements.

Any questions, please ask!

Thanks,

Owain

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Owain,

We are not going to read the rest of your blog on your web site. If you want the members of this forum to read your blog, that is great... you will publish it here, in this forum. This forum is not going to be used to facilitate "poaching" to bring traffic to your site, so you can sell your little iphone app.

Your product looks interesting and it sounds like you have some great ideas and content to share, but you will do it here on this forum. You are welcome to complete a proper signature with your companies link in it, but just trying to bounce our members out of our site to your web site to sell your little app. is a no go.

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HOW IS VOICE PRODUCED?

To produce voice air must first pass from the lungs, up through the wind pipe (which is called the trachea) and be pushed between the vocal cords on its way out through the mouth. The vocal cords are two thin structures made up of muscle, ligament and mucous membranes, inside the larynx that normally move symmetrically, from complete closure to a wide opening. The larynx (or voice box) sits at the top of the wind pipe where it can easily be felt in a man’s neck as ‘Adam’s apple’. To produce a vowel sound such as ‘ahhh’, as in the words ‘part’ or ‘start’, the vocal cords must come together to meet in the middle. In this position, air is forced between the vocal cords causing them to vibrate very quickly.

WHY MEASURE THE QUALITY OF YOUR VOICE?

If using your voice is important to you, then it’s very useful to be able to measure and monitor changes to its quality over time. Firstly, it will allows you to start to understand what exactly is affecting your voice. It could be that a particular food or drink makes our voice much worse or it may be that you’re not warming up properly before singing, for example. Without measuring the day to day changes in the quality of your voice, it’s very difficult to understand what to do or change to help make it better. Secondly, if you already have a problem with your voice and are considering or already receiving treatment, such as speech and language therapy, voice coaching or even surgery, it’s important to know whether that treatment is making your voice better or how quickly your voice is responding to treatment. One way of knowing how your voice is responding is to measure it’s quality before you start and then at regular intervals as you progress through your therapy.

HOW CAN YOU MEASURE THE QUALITY OF YOUR VOICE?

There are several ways to measure the quality of your voice. One way is to listen to it yourself. You will often be the first to know when your voice isn’t as good as usual. Your friends and family may also notice a change. Another way is to ask a voice specialist, such as a speech and language therapist or laryngologist who have been trained how to assess the guality of your voice, simply by listening to it.

Beyond simply listening, there are a number of measurements that we use to assess someone’s voice quality. The most commonly used test are the following:

(1) Pitch,

(2) Jitter,

(3) Shimmer,

(4) Reading Pitch Range,

(5) Singing Pitch Range.

PITCH (FUNDAMENTAL FREQUENCY F0)

The pitch, or perceived height of the tone of the voice is determined by the speed at which the vocal cords vibrate – the quicker they vibrate, the higher the pitch. The shorter the vocal cords, the faster they vibrate, and the higher the pitch. Men generally have a larger larynx and longer vocal cords than women, which explains why they typically speak at a lower pitch. We measure pitch as the number of vibrations each second and is given the units Hertz or Hz for short. A professional soprano can make her vocal cords vibrate as often as 1000 times each second by moving her larynx so that the vocal cords are stretched to reach the highest notes; an adult male’s vocal cords, on the other hand, will typically vibrate about 100 to 150 times each second during normal conversation.

JITTER

Jitter is a measure of the irregularities in the frequency at which the vocal cords vibrate. Even when one tries hard to sing a particular note and keep it at a constant pitch, there will always be slight irregularities in the speed at which the vocal cords are vibrating and hence the pitch over time. Singers can sometimes notice this when they’re tired for example. With training, singers work to minimize these irregularities, or Jitter, in their voice. There are several ways to calculate the magnitude of the Jitter and this is measured in OperaVOX as the percentage change in the frequency of consecutive vocal cord vibrations from their common average. The higher the Jitter and the more abnormal the voice sounds. High values of jitter (in excess of 1 or 2%) can indicate a problem with your voice such as throat inflammation for example. High Jitter can be caused by a number of conditions that affect the vocal cords, including nodules, polyps, and weakness of the laryngeal muscles. If you are a singer, you will want a very stable voice and therefore very low jitter measurements.

SHIMMER

Shimmer is calculated by measuring the change in loudness, or amplitude, over several sound waves generated by the vocal cords vibrating. OperaVOX measures the average (absolute) difference between the loudness of consecutive vocal cord vibrations divided by the common average. Shimmer is a measure of the irregularities in the loudness of a particular pitch over time. Even when one tries hard to sing a particular note and keep it constant, there will always be slight variations in its loudness over time. It is a measure for the short-term irregularities of vocal fold vibrations. In a similar way to Jitter, Shimmer is calculated by measuring the change in loudness, or amplitude, over several sound waves generated by the vibration of the vocal cords. OperaVOX measures the average (absolute) difference between the loudness of consecutive vocal cord vibrations divided by the common average. An increased Shimmer (above 3%, for instance) can be the result of a number of conditions that affect the vocal cords, including nodules, polyps, and weakness of the laryngeal muscles.

MAXIMUM PHONATION TIME (MPT)

The MPT is the maximum time in seconds that a person can comfortably sustain a vowel in pitch and loundness on one breath and without stopping. Vowel sounds such as ‘ah’ ‘ee’ or ‘oo’ can be used, and the best of three attempts is generally used as an estimate of the maximum phonation time. A healthy adult, male or female, would normally be able achieve a time of more than 20 seconds on average.

READING PITCH RANGE

A characteristic of natural speech is that pitch moves upwards and downwards. For instance, rising pitch is used to stress a syllable or to mark a sentence as a question whereas a downward shift would indicate a statement or command. The amount of pitch movement inside a syllable, word, phrase or sentence is called pitch range. Pitch movements may reflect the emotional state of the speaker and can also be affected by certain health conditions. Anger, but also joy, is often characterized by a wide pitch range whereas depression and sadness are associated with a narrow pitch range, which is perceived as a monotone voice. The reading pitch range refers to the maximum and minimum pitches that the user would produce while reading a passage.

SINGING PITCH RANGE

The singing pitch range is the range between the lowest and highest ‘musically useful’ notes a voice can produce while singing. The user is asked to select a vowel and and a comfortable pitch in the middle of their vocal range and gradually increasing their pitch to the maximum they can comfortably produce and subsequently gradually decreasing their pitch to the minimum they can comfortably produce. OperaVOX discards outliers and chooses the frequencies that were sustained for a reasonable period of time to calculate the minimum and maximum frequencies.

Comments and remarks from Prof. Dr. Hermann J. Künzel, Department of Phonetics, University of Marburg gratefully acknowledged.

References:

(1) Verdolini, K., & Ramig, L.O. (2001). Review: occupational risks for voice problems. Logopedics, Phoniatrics, Vocology, 26 (1): 37-46.

(2) Smith, E., Lemke, J., Taylor, M., Kirchner, H.L. & Hoffman, H. (1998). Frequency of voice problems among teachers and other occupations. J Voice Dec;12(4):480-8.

(3) Royal College of Speech and Language Therapists, 2011, London, UK, accessed 11 November 2011, <http://www.nhscareers.nhs.uk/details/default.aspx?id=288>.

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